We reviewed 52 cases of osteomyelitis of the calcaneum. The clinical symptoms and signs were well defined, but different and less dramatic than those of long-bone osteomyelitis. Blood cultures were positive in 41% of cases and tissue cultures in 91%. Routine haematological tests were of little value, and radiological changes were often delayed, and were absent in 12%. With early diagnosis, treatment with antibiotics alone was usually effective, but complications and chronic disease were more likely if there was delay. Early diagnosis is the key to successful treatment. We describe a new physical sign and consider that diagnosis is almost always possible by clinical methods.