For many interpreters, at least one of their working languages is a second language (L2), i.e. acquired after early childhood. The status of L1 and L2 in relation to each other is an issue which has often been neglected; much research on interpreting has tended to focus on the processes involved, i.e. comprehension and production, on a structureal or semantic comparison of the languages involved, but not on their relation to each other within one-language-user.Since the acquisition, storage and usage of L1 and L2 differ this must ultimately be taken into consideration when attempting to understand the processes involved in interpreting. In this paper, an attempt is made to indicate some areas within second language acquisition research which could be fruitful in this respect for research on interpreting.