We describe the analysis of muscle hypertrophy in complete quadriplegics after 6 months of treadmill gait training with neuromuscular electrical stimulation (NMES). We aim to evaluate the effect of treadmill gait training using NMES, with 30–50% body weight relief, on muscle mass. Fifteen quadriplegics were divided into gait (n=8) and control (n=7) groups. The gait group (GG) performed training, associated to partial body weight support, for 6 months, twice a week, for 20 min. Control group (CG) individuals performed only conventional physiotherapy, but did not perform gait training using NMES. Magnetic resonance imaging (MRI) was performed over quadriceps, at the beginning and after 6 months. The MRI was done to determine the average of cross-sectional area of the quadriceps. Moreover, a gray scale was used to separate the muscle from the conjunctive tissue (when the value is closer to 225, there is a higher amount of muscle tissue). After 6 months there was an increase of cross-sectional area in the gait group (from 49.81±9.36 to 57.33±10.32 cm2; P=0.01), but not in the control group (from 43.60±7.56 to 41.65 ± 9.44 cm2; P=0.17). The gray scale did not show significant differences after 6 months; however, the mean value of the gray scale inside the quadriceps in the gait group increased by 7.7% and in the control group decreased by 11.4%. Treadmill gait associated with NMES was efficient to promove quadriceps muscle hypertrophy in quadriplegics with chronic lesions even when a partial body weight support was provided.