Background: Developmental dysplasia of the hip (DDH) is common, affecting 7.3 per 1000 births in South Australia. Clinical screening programmes exist to identify the condition early to gain the maximum benefit from early treatment. Although these screening programmes are effective, there are still cases that are missed. Previous research has highlighted key risk factors in the development of DDH. Objective: To compare the risk factors of cases of DDH identified late with those that were diagnosed early. Methods: A total of 1281 children with DDH born in 1988- 1996 were identified from the South Australian Birth Defects Register. Hospital records of those who had surgery for DDH within 5 years of life were examined for diagnosis details. Twenty seven (2.1% ) had been diagnosed at or after 3 months of age and were considered the late DDH cases (a prevalence of 0.15 per 1000 live births). Various factors were compared with early diagnosed DDH cases. Results: Female sex, vertex presentation, normal delivery, rural birth, and discharge from hospital less than 4 days after birth all significantly increased the risk of late diagnosis of DDH. Conclusions: The results show differences in the risk factors for early and late diagnosed DDH. Some known risk factors for DDH are in fact protective for late diagnosis. These results highlight the need for broad newborn population screening and continued vigilance and training in screening programmes. Background: Developmental dysplasia of the hip (DDH) is common, affecting 7.3 per 1000 births in South Australia. Clinical screening programs exist to identify the condition early to gain the maximum benefit from early treatment. Although these screening programs are effective, there are still Previous studies have highlighted the key risk factors in the development of DDH. Previous research has highlighted key risk factors in the development of DDH. Methods: A total of 1281 children with DDH born in 1988 - 1996 were identified from the South Australian Birth Defects Register. Hospital records of those who had surgery for DDH within 5 years of life were for treatment details. Twenty seven (2.1%) had been diagnosed at or after 3 months of age and were considered the late DDH cases (a prevalence of 0.15 per 1000 live births). Various factors were compared with early diagnosed DDH cases. Results: Female sex, vertex presentatio n, normal delivery, rural birth, and discharge from hospital less than 4 days after birth all significantly increased the risk of late diagnosis of DDH. Conclusions: The results show differences in the risk factors for early and late diagnosed DDH. Some known risk factors for results are the need for broad newborn population screening and continued vigilance and training in screening programs.