Growth was assessed in 82 children with acute lymphoblastic leukaemia (ALL) who achieved complete continuous first remission following treatment. 34 received prophylactic cranial irradiation at a total dose over 2000 cGy (group I) and 48 at a dose of 1800 cGy (group II). Chemotherapy was given over two or three years and was more intense in group II. Both groups showed a similar significant decrease in height standard deviation score (SDS) over four years (group I -0·31, group II -0·39). 15 children in group I were followed to ten years and continued to show restricted growth with a mean height SDS decrease of -0·84 (range 0 to -1-7). The greatest reduction in yearly decrements in height SDS occurred in the first year after diagnosis. In both groups height SDS increased significantly on completion of chemotherapy. Thus chemotherapy protocols contribute to growth retardation in ALL. In most of these children the mean loss of height over ten years was not sufficiently great to justify long-term growth hormone (GH) therapy. © 1988.