The association between idiopathic inflammatory myositis and cancer is well recognized. Most descriptions have been of dermatomyositis-associated cancer, however, a few have been of polymyositis-associated adrenal cancer. Here, we report a 69-year-old man in whom polymyositis-associated adrenal cancer was diagnosed. The patient complained of difficulty with walking and with standing unassisted. Physical examination and electrophysiological studies revealed an abnormality of the proximal muscles. Serum levels of creatine kinase and lactic dehydrogenase were increased. Imaging studies showed a solid tumor measuring 14 x 9 cm in the retroperitoneum. After surgical excision of the tumor, including the left kidney, the serum levels of creatine kinase and lactic dehydrogenase normalized, and symptoms of myositis disappeared.