This paper presents a taxonomy based on pragmatic criteria which aims to establish the most relevant functions of silence in colloquial conversations in Spanish. With this end, we have analysed a corpus of spontaneous conversations of 15 hours in which 10 young informants with higher education (five women and five men) interact. The results of the study reveal at least four major types or macrofunctions of silence: 1. discursive, 2. structuring, 3. epistemological and psychological and 4. normative. These functions contain several microfunctions or pragmatic realizations (intensification, reformulation, turn of speak assignation, dissention, reflection, being cautious, etc.) that recur with special frequency in exchanges where young people participate.