The effect of short term (12 weeks) physical exercise on serum total testosterone level was evaluated in 30 young male adults, aged 18-27 years (mean age 21.67+2.26 years). These medical students, having sedentary life style underwent heavy exercise by attaining heart rate 125-150 beats/min on bicycle ergometer for 15 min on alternate day basis amounted to 670 kilopond metre per minute work done and percentage of VO_2max was 71+3. Pre-exercise serum total testosterone levels (5.49+1.31) of students were compared with those obtained after 1 week and 12 weeks of initiation of exercise. The serum total testosterone was measured by DRG Testosterone ELISA kit. After 1 week of exercise, a statistically insignificant decrease (5.488+1.32; P>0.05) was found while after 12 weeks of exercise, a statistically significant increase (6.41+2.28 P<0.05) was noticed between the pre-and post-exercise serum total testosterone levels. We conclude that short-term exercise produces an elevation in serum testosterone levels in young adults.