Twin girls presented with infantile cortical periostosis (Caffey's disease) at 2 and 3 weeks of age, respectively. This disorder initially involved their upper and lower limbs and resulted in fever, irritability and tenderness. X-rays showed extensive periosteal new bone formation. Multiple relapses occurred in the first year of life and during some of these relapses mandibular and clavicular involvement was noted. Prednisolone, 1 mg/kg per day, was used to treat relapses until 9 months of age. Indomethacin therapy at this age at a dose of 3 mg/kg per day allowed the cessation of prednisolone therapy and disease flares were thereafter infrequent and responsive to indomethacin.