Measurement of the length and width of the ligament of the head of femur (ligamentum teres) in 140 normal human fetuses between 12 weeks and term provides limits for growth changes in this structure. These observations provide no morphological evidence of a significant difference between males and females, or between the right and left sides, to explain the female and left hip preponderance reported in congenital hip disease. The ligament is shown to be variable in length, width, and shape, and it is not a distinctly linear structure through linearity may increase with age. Tests of femoral head mobility support the opinion that this ligament must play a role in fetal and neonatal hip joint stability. Weak correlation only was demonstrated between the ligament variables and acetabular depth, which suggests that ligament shape and socket shape are not closely related. Comparison of measurements from normal and 12 dysplastic or subluxated joints provides no evidence to support previous observations that this structure is unusually long in abnormal hip joints which are not frankly dislocated.