Aerial respiratory behaviour in Lymnaea stagnalis was operantly conditioned using a procedure that results in long-term memory (LTM) persisting for 1 but not 3 days. By manipulating the snails' post-training environment, i.e. preventing Lymnaea from performing aerial respiratory behaviour, memory persistence was significantly extended. Memory retention, however, is only extended if snails are prevented from performing aerial respiration in the same context in which they were trained. Snails trained in the 'standard' context but prevented from performing aerial respiration in the 'carrot-odor' context (and vice versa) did not extend their memory. These data are consistent with the hypothesis that forgetting is due to interfering events, that occur following learning and memory consolidation.