Ten cases diagnosed as epidermoid carcinoma arising in the sinus tracts of chronic osteomyelitis have been reviewed. In two cases there were histologically proved metastases. Attention has been called to the signs and symptoms associated with carcinomatous change. The investigation of such a patient includes roentgenographic study of the limb and chest and a search for metastases in the regional lymph nodes and liver. A biopsy will guide the management. The histological diagnosis may be difficult because of pre-existing and coexisting metaplasia and pseudoepitheliomatous hyperplasia, which simulate cancer. The benign group should have extirpation of the sinus tracts and eradication of the osteomyelitis. Patients with atypical pseudoepitheliomatous hyperplasia and epidermoid carcinoma should have amputation at an adequate level and biopsy of suspicious regional lymph nodes. None of the three deaths in this series could be attributed to epidermoid carcinoma arising in osteomyelitis.