In February 1999 a serious radiological accident occurred in Yanango, Peru, when a welder picked up an 192Ir industrial radiography source and put it in his pocket for several hours. This action resulted in his receiving a high radiation dose that necessitated the amputation of one leg. His wife and children were also exposed, but to a much less extent. The purpose of this report is to provide an account of the circumstances of the accident and its medical aspects. Contents: 1. Introduction; 2. Background information on the circumstances of the accident; 3. The accident; 4. The emergency response; 5. Medical treatment of the patient; 6. Dosimetric analysis; 7. Findings, conclusions and lessons to be learned.