Serum creatine kinase BB (CK-BB) on the 1st day of life was measured by radioimmunoassay in 37 very low birth weight (VLBW) infats, 14 severely asphyxiated infants and 24 controls. The 31 survivors from the two high-risk groups were followed up for 12 months or more. VLBW non-survivors (n = 14) had significantly higher mean CK-BB levels than survivors (n = 23), (P < 0.05). However, if only survivors were considered, CK-BB was a poor discriminator of outcome in either study group. First day serum CK-BB is not a useful predictor of neurodevelopment outcome in surviving high-risk infants.