American Go Association Rules - Summary

This is a summary of the AGA rules of play as interpreted by the BGA and is intended to highlight the main differences from previous rules used.


Wheneveryou pass you must hand a 'pass stone' to your opponent as a prisoner.

Ko and Superko

You must not play so as to re-create a previous board position that you created on a previous play.

Rule Violation

A move which violates the rules of ko, superko, self-capture, or alternation is an illegal move. Any other violation of the rules is an irregularity. It is assumed that any violation is made inadvertently. Please see the section Illegal and Irregular Moves for details.

Game End

Play pauses when both players pass in succession. You then attempt to reach agreement on all the stones that should be removed without further play.

If such agreement cannot be reached, then play resumes with the opponent of the last person to pass moving first. If the first two moves of a resumption are pass, then the game ends with all stones remaining on the board.

White Passes Last

Once agreement is reached, or the game ended on a total of 4 consecutive passes, White must make an additional pass if Black was the last to pass.

The Score

At the start of the game you can agree to use Territory counting or Area counting, and if you cannot agree, then Territory counting is used. Territory is defined as empty intersections surrounded by stones of the same colour. So eye points in seki count towards territory.

Illegal and Irregular Moves

The clock must be stopped while players attempt to resolve any issue surrounding rule violation. If there is any doubt or dispute as to how to proceed, please call the referee.

Illegal Moves

In the case of a failure of alternation, the phrase "illegal move" in this section refers to the whole sequence of two or more moves played consecutively by the offending player.

If you inadvertently make an illegal move and if the error is noticed immediately, unwind to the position before the illegal move and pass, handing a pass stone to your opponent.

If the illegal move is noticed after one or more intervening moves then, by mutual agreement, the players may rewind to the position before the illegal move. The offender then plays a legal move without handing over a pass stone.

If the players do not agree to unwind, then play continues as is, except that, in the case of self-capture, the relevant stones should be removed from the board and handed to the opponent as prisoners.

Irregular Moves

If you inadvertently make an irregular move then as soon as the error is noticed, fix the position as best you can to the satisfaction of you and your opponent. Here are examples of irregular moves with the commonly accepted fixes:

Failing to remove all the captured stones
Remove the stones and give them to the opponent as prisoners.

Removing stones that still have one or more liberties
Replace all the removed stones. The original 'capturing' stone stays on the board.

Placing handicap stones in the wrong position
If this is noticed immediately before White's first move then set the stones correctly. Otherwise just carry on.

Placing a stone on an occupied intersection
If noticed immediately, remove the stone from the board and it is then the opponent's turn to play. If noticed later just remove the stone from the board and return it to the owner's bowl.

Placing a stone ambiguously in between intersections
Ask the owner of the stone to please position it on its intended intersection.

Playing a stone of the wrong colour
If noticed immediately, replace the stone with one of the right colour and complete any consequent captures. If noticed later try and fix the board position as best as you can. Where there is any doubt, a stone count can be used to decide if in fact a stone of the wrong colour has been played.
Last updated Wed Jun 18 2008. If you have any comments, please email the webmaster on web-master AT britgo DOT org.