Thirty unselected females with proven osteomalacia were evaluated clinically, electromyographically and histopathologically for muscle dysfunction. Clinical evidence of myopathy was found in all the patients except one; the electromyograms were abnormal in 25 of them, and histopathological abnormalities, although slight and nonspecific, were seen in all the 17 patients who underwent muscle biopsy. Electromyographic findings revealed a myopathic pattern as evidenced by a significant reduction in motor unit potential duration and amplitude, and an increased percentage polyphasicity as compared to the controls. There was a complete absence of denervation potentials. The histopathological abnormalities were nonspecific and slight, and consisted of fatty infiltration, interstitial fibrosis, sarcolemmal nuclear proliferation and variation in muscle fibre thickness. A statistically significant reduction in motor nerve conduction velocities of the ulnar and peroneal nerves was found. It was considered that this reduction in the velocities was due to subclinical neuropathy. Our data suggest that myopathy, neuropathy and osteomalacia in our patients are due to nutritional deficiencies of multiple vitamins.