The effect of iced water on the length of time required for oral temperature measurements to return to baseline in adults at 8:00 a.m. and 4:00 p.m. was examined. Each of the 24 subjects participated at both times of the day and thus served as his/her own control. Using electronic thermometers and standardized iced water solutions, the mean length of time required for oral temperature to return to baseline after ingestion of iced water was 14.04 min at 8:00 a.m. and 10.25 min at 4:00 p.m. This difference was statistically significant, supporting the hypothesized temporal variation in the effects of iced water on oral temperature measurement. © 1993 John Wiley & Sons, Inc.