Chicks affected with hereditary muscular dystrophy were deprived of water for 1 to 4 days at ages to 37 days ex ovo. Water deprivation partially alleviated impaired righting ability and reduced the typically elevated plasma creatine kinase activity by as much as 90%. Muscles from water-deprived chicks showed several qualitative histologic improvements, including decreased sarcoplasmic staining for acetylcholinesterase activity, reduced fiber diameters, and a decreased incidence of abnormally large rounded fibers, but retained the high degree of fiber diameter variability characteristic of dystrophic muscles. Feed deprivation reduced body weight to a similar extent as water deprivation but had lesser effects on creatine kinase activity and did not improve righting ability or muscle histology. Although the mechanism of the improvements is unknown, the magnitude and scope of the effects suggest that water deprivation beneficially alters a major abnormality in dystrophic chickens.