Anthropometric characteristics, passive hip flexion, and spinal mobility were examined and back pain was registered in 116 top Swedish male athletes representing four different sports (wrestling, gymnastics, soccer, tennis). Differences in stature, body weight, passive hip flexion, mobility of the spine in forward flexion, and asymmetry of the back were found when each group of athletes was compared with the rest of the athletes. These differences could be explained by a natural selection of individuals with the physical constitution required for the sport concerned, but they may also be a long-term effect of training. A small sacral inclination, defined as the sacrohorizontal angle, correlated significantly with back pain.