Adult patients (greater than 18 years), referred to the Royal Marsden Hospital between 1974 and 1990 with embryonal tumours, have been reviewed. The aim of the study was to document the presentation, management and outcome for this group of patients and to compare these parameters with those of tumours of the same histology arising in the paediatric population. The study population consisted of 15 patients with medulloblastoma, 15 with Ewing's sarcoma, three with neuroblastoma, seven with rhabdomyosarcoma and two with nephroblastoma. Actuarial survival, at 5 years, for adults with medulloblastoma was 80%, which compares very favourably with the outcome for children treated over the same time span. In addition, salvage therapy after relapse was in some cases successful. In the Ewing's sarcoma group the outcome was less favourable, with 5-year actuarial survival of 50%. This is disappointing in view of the lack of tumours with poor prognostic features and may be an area in which these tumours differ from those that arise in children. The number of patients with the diagnosis of neuroblastoma, rhabdomyosarcoma and Wilms' tumour was too small for statistical analysis and they are presented as case reports. Embryonal tumours arising in adults provide an opportunity to study clinical behaviour and biology from an extreme standpoint. This may provide useful information with regard to aetiology, natural history and treatment response. The establishment of registers facilitate the collection of relevant data and also offers the opportunity to improve the treatment received by patients with these rare tumours.