Comprehension and production of spoken language are very memory-intensive tasks, especially in real-time natural interactions. Yet, it is well-known that human beings have a very limited capacity for retention of newly-presented material, a phenomenon normally attributed to limitations on short-term memory. This dissertation provides evidence that the Intonation Unit (IU), an intermediate-level prosodic phrase, serves a critical role in processing of spoken English by carving up the continuous speech stream into bite-sized 'chunks' that can be easily fit into listeners' limited focus of attention. Three empirical studies are presented: a study of memory span in terms of IUs, employing data from a verbatim recall experiment; a study of association strength between and across IU boundaries, employing data from the same recall experiment; and a study of priming duration in terms of IUs, analyzing a corpus of spoken English. The implications of the findings with respect to Wallace Chafe's (1980,1987,1994) conception of Intonation Units and theories of short-term memory are explored.