MRI in combination with three-dimensional reconstruction is pre-eminently suitable for the study of the human musculoskeletal system in vivo in an accurate and detailed way. MRI provides the possibility of studying superficial as well as deep muscles under tension in the living state. Bones, muscles, tendons and adipose tissue are clearly visible. Parts can also be distinguished within a muscle. After reconstruction of the 2-D images the geometry of the muscles and muscle parts can be visualized from different angles. This leads to a deeper understanding of the biomechanics and functional anatomy of the musculoskeletal system of the human body. In this paper the morphology of the muscles around the hip was studied in three subjects in vivo on the basis of three-dimensional (3-D) reconstructions of two-dimensional (2-D) MR images.