Literature on simultaneous interpretation (SI) contains many recommendations addressed to interpreters on the need to avoid pauses and interruptions in order to produce a more fluent high-quality delivery. Some questions still remain open as to whether such occurrences depend on the interpreter, situational constraints of SI or the source-text (ST). In order to start investigating this subject, ten interpretation students were asked to translate simultaneously two text excerpts of a spontaneous speech containing pauses, hesitations and interruptions. This study aims to analyse whether and to what extent the presence of such occurrences in the ST affects the interpreter’s comprehension and delivery. Occurrences in both ST and target-texts (TT) are described in an attempt to produce a taxonomy which can be applied to SI; pauses and interruptions are not seen as mere interruptions of fluency; whenever possible, their communicative value and/or tactical use are stressed.