This study compared the ergogenic effects of caffeine on men who were endurance trained to those who were untrained. The study was a double-blind, placebo-controlled crossover experimental design. Ten endurance trained men (mean age 24.4 ± 2.0 yrs, weight 79.4 ± 8.5 kg, predicted VO2 max 46.3 ± 1.8 mL·kg-1·min-1) and 10 untrained men (mean age 22.8 ± 1.9 yrs, weight 88.9 ± 9.9 kg, predicted VO2 max 37.6 ± 2.7 mL·kg-1·min-1) completed two cycle ergometer trials to exhaustion at 80% of their predicted workload max 30 min after ingesting either 5 mg·kg-1 of body weight of caffeine or a placebo. Neither group displayed significant increases in time to exhaustion (Trained Group: 786.4 ± 251.5 sec for the placebo trial and 810.7 ± 209.4 sec for the caffeine trial and the Untrained Group: 514.6 ± 107.8 sec for the placebo trial and 567.3 ± 140.5 sec for the caffeine trial) after ingesting caffeine. When compared statistically between groups, the difference was not significant. When the groups were combined, the difference was caffeine and the placebo was not significant. The findings indicate that there was no ergogenic effect of caffeine on time to exhaustion in either endurance trained or untrained men.