In order to understand the pathogenesis of mouse muscular dystrophy, fatty acid and lipid compositions in tongue and hindleg muscles of dystrophic mice were analyzed. The phospholipid contents in tongue and hindleg muscles were 71-73% and 23-24% of the total lipids, respectively. The content of triglyceride in tongue and hindleg muscles was 8% and 66% of the total lipids, respectively. There were no significant differences in the phospholipid content of the tongue or hindleg muscles between normal and dystrophic mice. However, analyses of the fatty acid composition in phospholipids showed that the content of 16:0 and 22:6 in the hindleg muscles of dystrophic mice decreased significantly, while the content of C-18 fatty acids (18:0, 18:1 and 18:2) increased. In addition, the fatty acid composition in phospholipids of tongues of dystrophic mice was identical to that of normal mice. This latter result supports the bone-muscle imbalance hypothesis for the pathogenesis of mouse muscular dystrophy.