Training and competitive epinephrine and norepinephrine levels and proportions were compared in two groups of women athletes to determine whether changes in catecholamine excretion reflect the added mental stress of athletic competition on physical effort. An intercollegiate basketball team and a group of track and field athletes volunteered as subjects. Competitive epinephrine urinary levels were significantly (P less than 0.01) higher than training levels. A concomitant rise in the norepinephrine with an increase in physical effort was observed in both groups of athletes following training sessions as well as after athletic competition. Track and field athletes trying to qualify for an international team exhibited significantly ( less than 0.01) higher epinephrine levels than the team members; thus suggesting that anticipation of competition imposes a mental stress on an athlete. Constant changes in the catecholamine pattern as against a normal work load have yet to be established.