Ultrasonographic study of 463 normal children (926 hips) from birth to 6 months of age with equal sex distribution was performed. Hip morphometry, including Graf's alpha and beta angles, Morin's head coverage percentage, and head size were measured. Using the same technique, a group of 52 babies was measured longitudinally from birth to 6 months of age, with three measurements taken for each hip for a total of 312 measurements. Results showed that the boys had a consistently higher alpha angle, a lower beta angle, better head coverage, and larger head size through the 6 months. Differences between the right and left hips were only noted in the beta angle. The containment of the hip was found to increase rapidly in the first 4 months. Comparing data from the longitudinal versus the cross-sectional group, no statistically significant differences were detectable in all the parameters measured. Intraobserver variations were found to be best with alpha angle measurements, with a standard deviation of 3.22°.