This paper presents the design and the evaluation of a method to study prosodic features of discourse structure in unrestricted spontaneous speech. Past work has indicated that one of the major difficulties that discourse prosody analysts have to overcome is finding an independent specification of hierarchical discourse structure as to avoid circularity. Previous studies have tried to solve this problem by constraining the discourse or by basing segmentations on a specific discourse theory. The current investigation first explores the possibility of experimentally determining discourse boundaries in unrestricted speech. In a next stage, it is investigated to what extent boundaries obtained in this way correlate with specific prosodic variables: the features pause, pitch range, and type of boundary tone are studied as a function of discourse structure.