Acol is the bridge bidding system that, according to The Official Encyclopedia of Bridge, is "standard in British tournament play and widely used in other parts of the world". It is a natural system using four-card majors and, most commonly, a weak no trump.

Origins

Acol is named after the Acol Bridge Club in London NW6, where it originated in the early 1930s. The club was founded on Acol Road, named after Acol, Kent. According to Terence Reese, the system's main devisers were Maurice Harrison-Gray, Jack Marx and S. J. "Skid" Simon. Marx wrote in the Contract Bridge Journal of December 1952, that "...the Acol system was pieced together by Skid Simon and myself the best part of 20 years ago." In another account, Marx and Simon... "progressively, infected and re-infected each other with the virus of the game. In interminable slow walks... they would wander round and round the quiet streets, endlessly discussing the refinements of the enthralling game. Out of these conversations—surely a strange gestation—was born Acol as we know it and play it to-day." The first book on the system was written by Ben Cohen and Terence Reese. Skid Simon explained the principles that lay behind the system, and the system was further popularised in Britain by Iain Macleod. 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 North America. Ely Culbertson and his partner Teddy Lightner had visited the Acol Bridge Club in 1934, after which members S.J. Simon and Jack Marx became interested in bridge bidding theory. Simon and Marx soon afterwards began a discussion that eventually led to the first version of the Acol system.

Bidding system structure

As a bidding system, Acol has the following characteristics:

Variants

Acol is an unregulated system. There is no Acol governing body and no single publication containing the "official" Acol (unlike, for example, Standard American Yellow Card). It can be compared to a living language since it is liable to change at the whim of users. The main versions of Acol in use today are:

Standard Acol

The following is a brief summary of the Standard Acol as from 2000 to 2005. Standard Acol has not changed significantly since that time.

Opening bids

Opening bids promise at least 12 high card points (HCP), or the equivalent in HCP and shape, unless preempting. Apart from NT, opening bids guarantee the ability to make a rebid over any forcing response from partner. There are six special opening bids which are quite closely defined, and one wide-ranging opening bid: The wide-ranging 1 of a suit bid is the most common opening bid, accounting for about 75–80% of opening bids. The 1NT opening occurs on about 20% of biddable hands if "weak", or 10% if "strong".

Responses to 1 of a suit

Note 1: these last three bids may conceal 4-card support for opener's suit, whereas the three NT responses deny 4-card support for opener, and also normally deny holding a 4 card major biddable at the 1 level Note 2: when supporting opener's suit with an 8-card fit or better, HCP ranges can be adjusted downwards slightly to allow for shortages (singletons or voids) ''Note 3: with at least four-card support for opener's major and 13+ HCP, bid a new suit and then jump to 4 of opener's suit on the next round, a delayed game raise. Alternatively, by partnership agreement, the Jacoby 2NT or an alternative method may be used.''

Responses to 1NT

The responses below assume a weak (12–14) NT opening: players should adjust the point ranges for responses if playing a different opening range.

Responses to 2NT

Responses to 2

Responses to 2 of a suit (strong two)

Opener's suit rebid after one-level opening

Rebid own suit

Bid new suit

Support for responder

Note: when supporting responder's suit with an 8-card fit or better, HCP ranges can be adjusted downwards slightly to allow for shortages (singletons or voids)

Opener's NT rebid after one-level opening

The following bids assume a weak (12–14) NT opening.

After a suit response at one level

The traditional rebids are: However, the modern approach modifies the ranges for the rebids thus:

After a suit response at two level

The traditional rebids are: The modern approach is to use the 2NT rebid as forcing to game with 15–19 points, allowing major suit fits to be found at the 3 level. 3NT may be used as 15–17 with support for the minor that responder has bid (one option). After the opener's 2NT rebid, 3 can be used as a (forcing) enquiry to seek definition of the 2NT rebid. The only non-forcing bid by responder after opener's 2NT rebid is a rebid of responder's suit. This means that bidding opener's first suit is unconditionally forcing.

Responder's second bid

By the time responder has to rebid, it is often clear what the best final contract should be, especially if either player has made a limit bid. If opener has bid two suits, responder can show preference between them. With a strong hand but uncertain whether a game contract is on or which game it should be, he can use fourth suit forcing to obtain further information.

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.

Overcalls and doubles

Suit overcalls promise at least 5 cards. Jump overcalls promise at least 6 cards, but may be played as weak, intermediate or strong. BfA Acol uses intermediate (opening hand, 11–16 points). 1NT overcall typically promises 15–18 points and at least one stopper in opponents' suit. Double is for takeout, showing an opening hand (12+ points) short in opponents' suit (occasionally a very strong hand, at least 16+ points, of other shapes)

Responses to 1 of a suit if opponents overcall

Generally similar to unopposed bidding, but with these differences:

Alternatives

In common usage, the term Acol is understood to refer to a four-card majors system. For hybrid systems using the weak NT opening with one or both five-card majors, a different terminology is preferable.