This study was conducted to examine the validity and reliability of the leg length measurements with a tape measure. The purpose of this study was to determine: 1) the validity of the leg length measurements through comparison with x-rays, and 2) the intertester reliability. Thirty healthy subjects between the ages of 18 and 65 were studied. Each subject was positioned supine on an x-ray table. A radiopaque ruler marked in 1 mm increments was placed on the table. Two physical therapists measured the right leg length of each subject from anterior superior iliac supine to medial malleolus with a pliable metal tape measure. X-rays were taken by the slit scanography method. Pearson product-moment and intraclass correlation coefficients (r and ICC, respectively) were used to analyze the data. The value of r for the comparison: 1) between therapists was 0.98, 2) between therapist 1 and x-ray measure was 0.98, and 3) between therapist 2 and x-ray measure was 0.98. The value of ICC for the comparison: 1) between therapists was 0.99, 2) between therapist 1 and x-ray measure was 0.99, and 3) between therapist 2 and x-ray measure was 0.99. The findings of this study indicate that the leg length measurements from anterior superior iliac spine to the medial malleolus with tape measure are valid and reliable. Hence, confidence can be placed in the accuracy of clinical measures. J Orthop Sports Phys Ther 1986;8(4):185-188.