This study observed biochemical changes that occur when an athlete's limb is immobilized for six weeks, and determined if electrical stimulation could alter any of these changes. A control group (n = 3) and a stimulation group (n = 6) who had undergone major knee surgery, consented to a series of muscle biopsies of the vastus lateralis muscle. Both groups engaged in standard rehabilitative procedures following cast removal. The stimulation group's therapy also consisted of electrical stimulation (f = 2500 Hz.) of the quadricep group. The results indicate that ATPase activity decreased in the control group during the immobilization period (from 0.321 +/- 0.095 mumoles Pi/mg./min. to 0.205 +/- 0.032 mumoles Pi/mg./min.) but not in the stimulation group (from 0.268 +/- 0.022 mumoles Pi/mg./min. to 0.296 +/- 0.073 mumoles Pi/mg./min.), p less than 0.05. The stimulation did not appear to have any effect on glycogen concentrations. It is suggested that electrical stimulation retards the decrements in biochemical characteristics of human muscle due to immobilization.