Acol is a bridge bidding system. It is the name of a road in Hampstead, London, where there was a bridge club in which the system started to evolve in the 1930s. It was popularised in Britain by Iain Macleod in his book "Bridge is an Easy Game", published in 1952. The Acol system is continually evolving but the underlying principle is to keep the bidding as natural as possible. It is common in the British Commonwealth but rarely played in America.

Bidding system structure

The choice between a weak 1NT opening (12-14 points, balanced) and a strong 1NT (15-17 points, balanced) influences much of the rest of the system.

Acol is an approach forcing system - whether or not a bid is forcing, i.e. systemically requires a response, depends on the previous bidding (approach). This is in contrast to level forcing systems, such as 2-over-1, where the level of the bid determines whether or not it is forcing.

It is also classified as a natural system, i.e. opening bids and responses almost always promise at least four cards in the suit. It is a four-card major system, unlike Standard American or European systems where, to open 1H or 1S, five cards in the suit are required.

Acol makes extensive use of limit bids. A limit bid is a bid which describes the hand in terms of both distribution and point count. A player making a limit bid has completely described his hand and may pass next round unless partner makes a forcing bid. A typical limit bid is the 1NT opening. Here the opener promises a limited point count (12-14 for a weak NT) and a particular distribution (4-3-3-3, 4-4-3-2 or 5-3-3-2). Responder now has a more or less complete picture of the partnership's combined strength and distribution and expects opener to pass any non-forcing and non-invitational bid.

Acol Variants

A version of Acol - called "Standard English" - has been developed by the English Bridge Union (EBU) to facilitate the learning of bridge and to provide a natural bidding system for novices and intermediate players. This system uses the Weak 1NT opening (12-14 points). Conventions such as Stayman and Blackwood convention are included. Players may choose to use Jacoby transfers as they progress their experience.

Benjaminised (Benji) Acol replaces the 2H and 2S openings with weak two bids (5-9 points and a 6 card suit). Any Acol 2 hand (8 winners with a given suit as trumps) is shown by bidding 2C which forces a 2D response allowing the suit to be shown. A 2D opener shows any hand with 23+ points.

Reverse Benji is the same as Benji except that the 2C and 2D bids are switched over. 2C is now the strongest bid as in standard Acol.

Standard Acol

The following is a brief summary of Standard Acol.

Opening bids

Opening bids promise at least 12 high card points (HCP), or the equivalent in HCP and shape. Apart from NT, opening bids guarantee the ability to make a rebid over any forcing response from partner.

• 1 of a suit - promises at least four cards in the suit bid. Not forcing.
• 1 NT - balanced hand (4-3-3-3, 4-4-3-2 or 5-3-3-2). Subject to partnership agreement, it may be either 12-14 HCP (weak), 15-17 or 16-18 HCP (strong) or vary between weak and strong according to vulnerability (variable). Limit bid.
• 2C - conventional game forcing bid, promising game-going values (normally 23+ HCP) and at least 5 quick tricks. Game forcing unless opener rebids 2NT.
• 2 of any other suit - shows a strong hand with at least eight playing tricks. Forcing for one round.
• 2NT - balanced hand, 20-22 HCP. Limit bid.
• 3 of a suit - preemptive, normally seven or more cards in the suit bid (may be six at favourable vulnerability), weak hand (not more than 10 HCP). Not forcing.
• 3NT - to play. Normally opener has a long solid minor suit. (Gambling 3NT)

Responses to 1 of a suit

• pass - less than 6 HCP
• 2 of opener's suit - at least four card support, 6-9 HCP. Limit bid.
• 3 of opener's suit - at least four card support, 10-12 HCP. Invites game if opener has requisite strength (14 HCP or more). Limit bid.
• 4 of opener's suit - at least four card support, to play.
• 1 NT - 6-9 HCP, denies ability to bid at 2 level. Not necessarily balanced. Limit bid.
• 2 NT - balanced, 10-12 HCP. Limit bid.
• 3 NT - balanced, 12-15 HCP. Limit bid.
• 1 of a new suit - promises at least four cards in the suit bid, 6 HCP upwards. Forcing for one round.
• 2 of a new suit (below 2 of opener's suit) - normally 5 card suit, at least a good 8 or 9 HCP. Forcing for one round.
• Jump in a new suit - 5 card suit (or support for partner), at least 16 HCP, Game force.

Responses to 1 NT

• 2C - Stayman. Opener responds 2D with no four card major, 2H with a four card heart suit and 2S with four spades (denies four hearts). Forcing for one round.
• 2 of any other suit - to play. Opener must pass.
• 3 of a suit - shows a five card suit, forcing for one round.
• 2NT - 11-12 HCP. invites game if opener is maximum (i.e. for a weak opening NT, if opener has more than a good 13 HCP).
• 3NT - to play.
• 4C - asks for aces. (Gerber)
• 4H, 4S - to play.
• 4NT - Slam invitation to 6NT. Opener bids 6NT with a maximum.
• 5NT - Slam invitation to 6NT. Opener bids 6NT unless a minimum. (Some play as invitation to 7NT; opener bids 6NT if minimum, 7NT with a maximum).

Responses to 2 NT

• 3C - Baron. Opener bids his lowest four card suit. Forcing. (Stayman may also be used as in responses to 1NT, i.e. 3D shows no 4 card major)
• 3 of other suit - shows a five card suit, forcing to game.
• Other responses as over 1NT.

Responses to 2 C

• 2D - negative. Responder lacks the strength for a positive response. Unless opener rebids 2NT (balanced, 23-24 HCP, which may be passed), the sequence is forcing to game.
• 2NT - fairly balanced, 8 or more HCP. Forcing to game.
• 2 of a suit - at least five in the suit, the equivalent of an ace and a king in high cards. Forcing to game.
• 3 of opener's suit - 5-8 HCP, at least 3 card support. Forcing to game.
• 3 of a suit - Solid suit of at least six cards. Forcing to game.

Responses to 2 of a suit

• 2NT - negative. Responder lacks the strength for a positive response.
• Simple bid of a new suit - 8 or more HCP, at least five in the suit. Forcing to game.
• 3 of opener's suit - 5-8 HCP, at least 3 card support. Forcing to game.
• 3NT - flat hand, 8-11 HCP. Not forcing.

Opener's suit rebid after one-level opening

• Rebid of own suit at lowest level - minimum hand, at least a five card suit, 12-15 HCP, non-forcing.
• Jump rebid of own suit - strong hand, normally at least 6 card suit, 15-19 HCP, non-forcing but highly invitational.
• Bid of new suit at lower level than first suit - minimum hand, 12-15 HCP, first suit has at least as many cards as second suit, non-forcing.
• Bid of new suit at higher level than first suit ("reverse") - strong hand, 16-19 HCP, first suit has more cards than second suit, forcing for one round.
• Jump in new suit at lower level than first suit - strong hand, 16-19 HCP, first suit has at least as many cards as second suit, forcing for one round.

Opener's NT rebid after one-level opening

(The following bids assume a weak NT opening)

After suit response at one level the traditional rebids are:

• 1NT - balanced, 15-16 HCP, limit bid
• 2NT - balanced, 17-18 HCP, limit bid
• 3NT - balanced, 19 HCP, limit bid

However, the modern approach modifies the ranges for the rebids thus:

• 1NT - balanced, 15-17 HCP, limit bid
• 2NT - balanced, 18-19 HCP, limit bid
• 3NT - Often an Acol two type of hand prepared to play in NT.

After a suit response at two level the traditional rebids are:

• 2NT - balanced, 15-17 HCP, limit bid
• 3NT - balanced, 18-19 HCP, limit bid

The modern approach is to use the 2NT rebid as forcing and use 3NT as 15-17 with support for the minor that responder has bid (one option).

After the 2NT (forcing) rebid, either bid naturally or use an enquiry (3c) to seek definition of the 2NT rebid.

Fourth suit forcing

A bid of the fourth suit at the 2 level by responder is a one round force, usually asking opener to bid no trumps with a stopper in the fourth suit. A fourth suit bid at the 3 level is similar, but forcing to game.