White Muscle Disease (WMD) is a well-recognized degenerative muscle disease found in neonatal lambs. Pathogenesis is by deficiency of selenium and/or vitamin E. Morbidity and mortality in young lambs is common in areas where selenium and/or vitamin E are deficient. Arizona is not known as a deficient area yet older lambs are diagnosed with WMD during the hot summer months. Lambs affected with WMD cannot be brought to market and are a major economic concern for Arizona producers. We propose that the extreme heat experienced in central Arizona creates an unusually high demand for vitamin E not seen elsewhere. We propose this condition be termed Heat Stress Syndrome. Little is known about the prevention of heat induced WMD or Heat Stress Syndrome. This study will review the records of a local producer to investigate the efficacy of prophylactic megadose vitamin E treatment of vitamin E in reducing Heat Stress Syndrome (HSS). Specifically, the question of whether prophylactic treatment with vitamin E reduces the incidence of HSS in older lambs will be addressed. Such therapy options would be a welcome addition to the veterinarian's therapeutic portfolio and of economic interest throughout the region.