Analysis of three cases and a review of the recent literature on squamous cell carcinoma arising in osteomyelitis confirm that this is an uncommon condition which may run a less benign course than was earlier believed. The disease affects chiefly middle-aged and older men, usually involves the lower extremity and most often occurs in the tibia. Development of a malignant tumour is heralded by increased pain and foul-smelling drainage in the presence of a fungating ulcer. Increased bone destruction is seen on the roentgenograms. A consistent finding is the long duration of infection but the authors stress that sinus drainage of long duration is not essential: the carcinoma can arise in scar overlying quiescent osteomyelitis as is occasionally seen in burn scars. Amputation is the treatment of choice.