After successful bone-marrow transplantation (BMT) in thalassaemia, the individual acquires the pattern of globin synthesis of the donor. We call such an individual "ex-thalassaemic after BMT", a term that underscores the cure of the genetic defect but maintenance of residual signs of organ damage due to iron overload and dysfunction acquired during the pretransplant years. We have analysed the extent and fate of tissue iron overload in 151 ex-thalassaemic patients after BMT, according to the risk factors of hepatomegaly, hepatic portal fibrosis, and inadequate chelation therapy. Serum ferritin concentrations decreased and unbound iron binding capacity (UIBC) increased slowly during the years after the transplant. When analysed according to risk group (assigned at the time of the transplant), ferritin and UIBC returned within the normal ranges in only the low-risk group (without hepatomegaly or portal fibrosis, and with adequate chelation pre-BMT). Ferritin and UIBC were still abnormal 7 years after the transplant in the moderate-risk group (those with one or two risk factors) and highly abnormal in the high-risk group (all three risk factors) indicating persistence of, respectively, moderate and severe iron overload at the time of transplant. In ex-thalassaemic patients who were studied before and yearly after the transplant the extent of haemosiderosis, as judged by staining of liver biopsy samples, decreased during the years after transplant. The degree of iron deposition and rate of post-BMT linear growth seem to influence rate of post-BMT decrease in tissue iron overload in different risk groups at the time of BMT.