SRI collected a corpus to study how spontaneous speech differs from other types of speech. The corpus was collected in two parts: (1) a spontaneous Switchboard-style conversation on an assigned topic, and (2) a reading session in which participants read transcripts of their conversation from part 1. Experiments were conducted on sentences with identical transcripts that varied in speaking style. The word-error rates varied from 29% (careful dictation) to 53 % (spontaneous conversation) depending on the speaking style. These experiments show that speaking style is a dominant factor in determining the performance of large-vocabulary conversational speech recognition (LVCSR) systems. 1.