Originally posted by SweettuffFrom the FAQs
My opponent and I keep jockying between the same two sqaures unwilling to change our tactic. Is there a limit to the number of times one can switch between two positions?
Third repetition of a position. If any identical position appears three times during a game, then the game can be claimed as a draw. Please note that each repetition must be identical with regards to en passant and castling availability. A draw can only be claimed along with a move that contributes to a repetition. Claiming after the repetition has occurred is not possible, unless the same position can be repeated again on a future move.