Objective: To determine whether the addition of electrical stimulation to progressive resistance training increases the voluntary strength of the wrist muscles in people with tetraplegia. Design: Assessor-blind within-subject randomised controlled trial. Setting: Two Australian spinal cord injury units and the community. Participants: Sixty-four wrists of 32 people with tetraplegia and bilateral weakness of the wrist extensor or flexor muscles (grade 2 - 4 Medical Research Council grades). Interventions: Participants' wrists were randomly allocated to one of two conditions. Wrist muscles of the experimental arm received electrical stimulation superimposed on progressive resistance training. The wrist muscles of the contralateral arm received sham electrical stimulation superimposed on progressive resistance training. Both arms received 6 sets of 10 contractions three times a week for eight weeks such that the only difference between arms was the application of electrical stimulation. Main Measures: The primary outcome was maximal voluntary isometric strength. Secondary outcomes were a fatigue resistance ratio representing voluntary and electrically-stimulated endurance. Measurements were taken at the start and end of the eight-week treatment period. Results: The mean treatment effect (95% Confidence Interval) of electrical stimulation for voluntary strength was 0.04 Nm (95% CI, -0.5 to 0.6; p =0.89). The mean treatment effect (95% CI) for fatigue ratio representing voluntary endurance and electrically-stimulated endurance was -0.01 (95% CI, -0.1 to 0.1; p =0.78) and -0.07 (95% CI, -0.3 to 0.1; p =0.47), respectively. Conclusions: Voluntary strength of the wrist is not enhanced by the addition of electrical stimulation to progressive resistance training programs in people with tetraplegia.