The reliability of Graf's technique in diagnosing developmental dysplasia of the hip (DDH) is investigated in this report. In a prospective study, 6,548 neonates were examined clinically and sonographically; 470 children were reexamined at least once. Sonographic a angles and radiographic acetabular index (AI) angles were followed up and compared. Results were as follows: 84.6% of the hips were mature; 14.3% were physiologically immature; 1.1% were dysplastic. Of the sonographically dysplastic hips, 63% were clinically normal. Neonatal sonographic hip status was affected by family history, breech delivery, birth weight, and gestational age. At follow- up, none of the primarily mature hips had worsened. Of the type Ha hips, 89% matured spontaneously, and 11% needed abduction. The 68 dysplastic hips had matured after a maximum of 80 days' abduction, with normal α and AI angles by the end of treatment. At 1 year, the pitch had deteriorated again in six children. Grafs sonographic technique reliably diagnoses infantile DDH. Regular orthopedic checkups are needed to detect secondary deterioration of dysplastic hips.