The author aims to provide a brief summary of the neurolinguistic processes involved in simultaneous interpreting within the framework of his so-called ‘subset hypothesis’ according to which the bilingual’s – and thus the interpreter’s – two languages are characterized as subsystems of language competence, which in the author’s view of part of and different from the larger cognitive system. He details in hypothetical form the complexity of the simultaneous interpreting task, inferring that, at points, four cognitive tasks are processed concurrently.