To examine the relation of dementia severity to the quality and quantity of oral discourse of individuals with Alzheimer disease (AD), a picture description task was administered to elicit oral discourse samples from 63 AD subjects, five individuals with very mild cognitive impairment, and 52 normal controls. Eight measures of discourse were used: total words, information units, conciseness, circumlocutions, frustrations, aborted phrases, revisions, and ideational repetitions. Information units, which decreased with increased dementia severity, proved to be the best measure for evaluating the effects of AD on oral descriptive discourse. The conciseness index also decreased with increased dementia severity, and a significantly greater proportion of AD discourse samples contained ideational repetitions. Circumlocutions and frustrations rarely occurred, and although the discourse of AD subjects was more likely to contain an aborted phrase, the frequency of aborted phrases did not vary by stage of dementia. Revisions were commonly observed in the discourse of both normal controls and AD subjects and did not differentiate the two groups.