Buruli ulcer is a severe necrotizing cutaneous infection due to Mycobacterium ulcerans. The disease is currently expanding, especially in West Africa, and the WHO is supporting a vast research program to better understand the modes of transmission, to develop diagnostic methods, and to define specific treatment protocols. The disease transmission could be linked to environment and especially water striders. After M. ulcerans inoculation, cutaneous lesions appear, as broad painless ulcers, and thus ignored by patients. The production of mycolactone, a toxin, only virulence factor known at this time, is responsible for the cytotoxic effect on skin tissues. Complications may occur, especially super infections and more rarely bone involvement responsible for osteomyelitis. The prognosis is usually functional with sometimes severe sequels, and skin and tendinous retraction as well as amputation are frequent. The diagnosis is usually made on PCR but this is difficult in developing countries, direct examination is not very reliable, and culture is long and difficult. The disease often remains ignored and undiagnosed, leading to evolved clinical presentations and sequels. The treatment is not defined yet. It is often surgical exeresis with skin graft, not always efficient. Antibiotic combination protocols are under evaluation.