The purpose of this prospective, randomized study was to evaluate the efficacy of low-dose heparin, alone or in combination with electric stimulation, in the prevention of deep vein thrombosis (DVT) in C2 to T11 motor complete and incomplete-preserved motor, nonfunctional spinal cord injured patients. The tibialis anterior and gastrocnemius-soleus muscle groups were stimulated bilaterally, using 50 microsecond pulses given at 10Hz with a four-second "on" and an eight-second "off" cycle for 23 hours daily over a 28-day period. Forty-eight patients, less than two weeks after injury, were randomly assigned to saline placebo (n = 17), low-dose heparin (5,000U, subcutaneous every eight hours) (n = 16), and low-dose heparin plus electric stimulation (n = 15). A normal 125-I fibrinogen scan and impedance plethysmography were required for entry into the study. Surveillance for DVT was evaluated by daily 125-I fibrinogen scanning. Venography was performed to confirm a positive impedance plethysmography and/or 125-I fibrinogen scanning tests for two consecutive days and at the completion of the study. The incidence of DVT was 8 of 17 in the placebo group, 8 of 16 in the low-dose heparin group, and 1 of 15 in the electric stimulation plus low-dose heparin group. The use of electric stimulation plus low-dose heparin significantly (p less than 0.05) decreased the incidence of DVT compared to the other treatments.