The purpose was to investigate time of day on responses to two types of exhaustive cycle ergometer tests. Sixteen males performed six exercise tests: three - constant power protocol and three - incremental protocol. The first test was a learning trial; the other tests were performed one in the morning and one in the afternoon. ANOVA revealed that O2 deficit and lactate were higher in the afternoon than the morning. Regardless of test type, time to exhaustion tended to be higher in the afternoon. VO2max was unaffected by the time of day and test type. These results confirmprevious reports of a time of day effect on anaerobic capacity, and support the contention that V02max is stable about a day.