The purpose of this study was to describe the effects of caffeine ingestion on the metabolic responses during submaximal exercise. Ten male of rowing player aged 18-22yrs. participated in the study. No subjects had any remarkable medical history and none were taking medications. According to the administration of dehydrated caffeine(CA) (6mg/kg) or placebo(PA), they were classified into two groups such as caffeine group and placebo group. A randomized, double-blind, crossover protocol was employed using either CA or PA. Subjects underwent a submaximal bicycle ergometer. Blood was drawn intravenously prior to 60 min., at rest, at 30, and 45 min. of exercise, and recovery period. Plasma concentrations of glucose, free fatty acid and lactate were obtained using enzymatic method. Followings were obtained by the tests and analyses; 1) Blood glucose(BG) of 45 minute of exercise was significantly decreased in CA group of 76.3$pm$14.8 mg/100ml compared with PA group of 94.9$pm$11.2 mg/100mg(p<0.5). 2) Free fatty acid(FFA) of 30minute of exercise was significantly increased in CA group of 720$pm$80 $mu$Eq/1 compared with PA group of 360$pm$120 $mu$Eq/1(p<0.5). After exercise, FFA was significantly higher in CA group than those in PA group(p<0.1). 3) Blood lactate(BL) was not significantly different between the two. After exercise, BL was significantly different in 30 minute(p<05).