OBJECTIVE: To examine the long-term outcome of early abduction splinting versus active sonographic surveillance in newborns with mildly dysplastic hips. PATIENTS AND METHODS: Between 1997 and 2003, 128 newborns with mildly dysplastic and potentially unstable hips on ultrasound (43° ≤ α-angle < 50°) were randomly assigned to immediate abduction treatment or sonographic surveillance. All were invited for a radiographic follow-up at 6 years. The radiographs were analyzed by a single radiologist masked to the randomization allocation, and markers of hip dysplasia (acetabular index, center-edge angle of Wiberg) and avascular necrosis were reported. RESULTS: Eighty-three participants (65%) agreed to participate in the follow-up (42 participants from the treatment group). The mean acetabular index was 14.7° (SD: 5.6°) for the treatment group and 13.9° (SD: 3.9°) for the control group (mean difference: −0.8° [95% confidence interval: −2.9° to 1.3°]). Values were within normal ranges for age for all participants except for 1 female subject from the treatment group. The mean center edge was 26.6° for those treated and 26.4° for the active surveillance group (mean difference: −0.3° [95% confidence interval: −2.5° to 2.0°]). None had markers suggestive of avascular necrosis. CONCLUSIONS: We found no difference in radiographic outcome at 6 years of age between children allocated to initial splintage for 6 weeks and those offered active sonographic surveillance. The delayed acetabular ossification or persistent dysplasia seen in a third of infants from both groups at 1 year of age had completely resolved in all but 1 of the female subjects from the treatment group.