Text types encountered in simultaneous interpreting (SI) often display blurred boundaries between written and spoken texts. Therefore the author suggests a text typology for SI should also deal with: 1) the medium of production, distinguishing written texts from texts directly generated in the spoken medium; 2) the functional content of the text; 3) the complementary use of language and non-language; 4) the speaker’s command of the source language; 5) the intertextual relationships a conference text enters. The author focuses specifically on this last parameter and distinguishes three types of intertextual relationships, viz. overlapping, contiguity and complementarity. Overlapping results in intertextual redundancy and involves retention of information from previously interpreted texts. A small-scale study consisting of rounds of secret enquiries with experienced interpreters confirms this hypothesis. Retention and prompt recall can play an important role in the optimization of SI and confirms the necessity of tests for an early diagnosis of a candidate’s aptitude.