A birth cohort of 3289 babies was investigated prospectively for one year to assess the importance of risk factors for congenital dislocation of the hip (CDH). 426 (13%) babies had an identifiable risk factor when examined by paediatric senior house officers. On further examination in the first week of life at a screening clinic, 51 proved to have CDH, an incidence of 15.5 per 1000 births. The results confirmed the importance of established factors such as family history, caesarean section, and the breech position, and demonstrated the clinical significance of the presence of clicking hips on initial examination. After up to 4.1 years of follow-up there have been no late presentations. By taking into account the clinical examination by senior house officers, secondary screening of babies at high risk of CDH can be very effective. This extended high risk group may contain all potentially abnormal hips. All such babies should be examined by ultrasonography in hospitals where it is available.