We recorded the incidence and degree of posterior subcapsular cataract (PSC) in 29 children who had undergone autologous (n = 28) or syngeneic (n = 1) bone marrow transplantation (BMT) due to haematologic or lymphoid malignancy. Conditioning prior to transplantation consisted either of a combination of chemotherapy and total body irradiation (TBI) (n = 21) or of chemotherapy only (n = 8). TBI was given in one fraction of 7.5 Gy. Nine patients had received previous cranial irradiation. The patients were followed for 4-10y (median 8 y) after transplantation. Of 29 patients, 22 developed PSC, all within 4 y after BMT. With the exception of one patient who developed unilateral PSC, all had received TBI. Conversely, 100% of those who received TBI developed PSC. In this group (+TBI), eight patients (38%) developed significant PSC, defined as best corrected visual acuity <0.8 in either eye. Six patients (10 eyes) have since needed surgical repair consisting of extracapsular cataract extraction and intraocular lens implantation. There was no clear relationship between previous cranial irradiation and cataract development, nor any other obvious baseline differences between those in the +TBI group who developed significant PSC and those who did not. Although effects of previous therapy cannot be ruled out, TBI appears to be the main cause of PSC in this group of patients. Twelve patients in the +TBI group had well-preserved visual acuity throughout the study, reflecting a slow progression of PSC. This compares favourably with previous reports of allogeneic BMT, possibly owing to less need for corticosteroids after autologous BMT. We conclude that the incidence of PSC was high after autologous BMT where the conditioning regimen included total body irradiation.