A male child with vertically transmitted human immunodeficiency virus type 1 (HIV) infection developed a Ewing's sarcoma of the left fibula at 6.1 years of age. We report the antitumour chemotherapy given and the response of the tumour. Six months after tumour diagnosis the child died of probable HIV encephalopathy. This is the first reported case of Ewing's sarcoma in an HIV-infected child.