We report a case of peripheral primitive neuroectodermal tumour (PNET) in a 36-year-old man who 10 years earlier received an allogeneic bone marrow transplantation (BMT) for a non-Hodgkin's lymphoma. Immunohistochemistry proved definitive elimination of a relapse of the original disease and confirmed the diagnosis of PNET. The role of total body irradiation pre-BMT in the genesis of this secondary tumour is discussed. The importance of registering secondary malignant solid tumours after BMT is emphasized. To our knowledge, an Ewing family tumour following BMT has not previously been reported.