In this paper, we analyse the gestural production of two Italian female adults in a spontaneous speech-context. Our analysis concerns with a specific gestural category, namely that of illustrative gestures, which have been analysed according to the following patterns: occurrency and time-relation with respect to speech and formal elements as movement of head, face, body and hand. In this way, we obtained a corpus consisting on 561 illustrative gestures. The analysis highlighted a particular fact: some gestures occurring with different verbal expressions present interesting formal analogies, suggesting the existence of what we have called gestural semantic fields . Our work shows how gestures can be organized, at a deep semantic level, in semantic fields, presenting an autonomous structure with respect to speech and, at the same time, allowing us to catch underlying, implicit semantic analogies between lexical items and concepts, otherwise not evident at the speech level.