Metabolic bone disease (MBD), or rickets, is common in very low birthweight infants. A descriptive, cross-sectional, hospital-based study was carried out at Muhimbili Medical Centre, Dar-es-Salaam from 15 April to 30 June, 1995 to discover the magnitude, contributory factors, morbidity and suitable biochemical diagnostic tests for MBD. One hundred infants with a postnatal age of 6-12 weeks, whose birthweights were 1500 g or less were studied. Thirty-three of 100 (33%) infants, 16 boys and 17 girls, were radiographically diagnosed as having metabolic bone disease. The mean (SD) gestational age of those infants was 30.4 (2.7) weeks, while that of the infants without metabolic bone disease was 32.4 (3) weeks (p = 0.003). There was no significant difference in birthweight, serum calcium and serum phosphate levels between those infants with MBD and those without. The mean (SD) serum alkaline phosphatase in infants with MBD was 1052.9 (493.3) U/l and 766.8 (301.7) in those without MBD (p = 0.006). Thus, metabolic bone disease is common in very low birthweight infants. Wrist radiography and serum alkaline phosphatase levels remain important diagnostic tools. MBD should be considered seriously in very low birthweight infants.