Sensory-motor and cognitive functioning was investigated in a group of 32 children treated with bone marrow transplantation (BMT), 1-6 years after treatment. Twenty-five of the patients had suffered from leukemia. The BMT procedure had involved a regimen of cytostatic drugs and, for leukemia patients, total body irradiation at a dose of 10 Gy, administered in one session. Cytostatic drugs and irradiation are known to be potentially neurotoxic, particularly when combined. The examination involved four neuropsychological tests of sensory-motor and cognitive functioning, as well as an age-appropriate intelligence test. For control the bone marrow donors (n = 32), siblings of the patients, were also investigated. A pronounced delay in motor development was found in four children, who had been treated with BMT including total body irradiation before 3 years of age. Patients between 3 and 11 years of age at BMT were at a slight disadvantage, compared to donors, on tasks involving perceptual and fine motor speed. In older patients no deficits were observed.