Abstract: 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.