Seven sedentary men (mean age, 22.5 yrs) were studied during and after treadmill exercise at 65% VO2max to determine the effect of a typical acute exercise bout on serum triglycerides. A venous blood sample was drawn immediately prior to a 30 minute treadmill exercise session, 5 min, 24 and 48 h after exercise. There were no significant differences in triglycerides and total cholesterol between the selected blood sampling points. Total HDL-C was higher (p < 0.05) at 5 min (44.0 SE +/- 3.0 mg.dl-1) than pre-exercise (41.5, SE +/- 3.0 mg.dl-1). Total HDL-C did not differ between pre-exercise and both 24 and 48 h. Unlike prolonged heavy exercise, a typical exercise session does not bring about alterations in serum triglycerides.