The purpose is to develop and demonstrate a rapid whole-body MRI method for automatic quantification of total and regional lean skeletal muscle volume. Quantitative water and fat separated image volumes of the whole body are manually segmented and used as atlases. The atlases are non-rigidly registered onto to a new image volume and the muscle groups are classified using a voting scheme. A leave-one-out approach with subjects scanned in a 1.5 T and a 3.0 T scanner is used for validation. The method quantifies the whole-body skeletal muscle volumes and the volumes of separate muscle groups independently of image resolution.