Objective: To evaluate muscular performance and appearance in patients with prior stroke who were ambulatory. Design: Nonrandomized study. Setting: University hospital laboratory. Subjects: Sixteen persons (11 men, 5 women) with minor motor impairments, 6 to 24 months after stroke, were included. As reference, data were used from a population-based sample of 144 men and women. Main Outcome Measurements: Muscle performance was evaluated using a Kin-Com dynamometer in both the affected and the nonaffected leg, Peak isometric strength was measured at a 60 degrees angle in both extension and flexion, Maximal isokinetic strength was measured at 60 degrees/sec and at 180 degrees/sec. Endurance was evaluated during isometric and dynamic knee extensions. Muscle biopsies were taken on nine patients and muscle tissue areas were determined with computed tomography, Results: The affected leg was weaker but not different in relative endurance compared with the nonaffected side. The performance of the nonaffected side was somewhat lower than that of a matched reference population. No major difference in fiber composition between the affected and nonaffected legs was noted, except for a lower degree of capillarization in the affected leg. Conclusion: In well-functioning stroke patients with good motor performance, further muscle training that includes resistance exercise might be indicated. (C) 1999 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation.