A total of 295 introductory psychology students rated descriptions of selected voice characteristics for either a distinctive or a non-distinctive voice heard for 36 seconds and retained for a maximum of 1 week. Subjects were randomly assigned to 1 of 4 delay conditions: a perception condition; an immediate memory condition; a 24-hour delay condition; and a 1-week delay condition. Distinctive voices differed from non-distinctive voices on each of the 10 characteristics at the 0.01 level of confidence: rate of speech; rate variation; pitch; expressive style; age; enunciation; inflection; tremor; pauses; and nasality. The results show that descriptions of distinctive voices were reliable over a 1-week retention period except for the rate of speaking. In contrast, descriptions of non-distinctive voices were more adversely affected by the length of the retention interval. These findings indicate that witness descriptions of non-distinctive voices should be given, if possible, within 24-hours of an incident. 2 tables and 23 references (Author abstract modified)