Muscle fibre type is a heritable trait and can partly predict athletic success. It has been proposed that polymorphisms of genes involved in the regulation of muscle fibre characteristics may predispose the muscle precursor cells of a given individual to be predominantly fast or slow. In the present study, we examined the association between 15 candidate gene polymorphisms with muscle fibre type composition of the m. vastus lateralis in 55 physically active healthy men. We found that rs11091046 C allele carriers of the angiotensin II type 2 receptor gene (AGTR2; involved in the skeletal muscle development, metabolism and circulatory homeostasis) had significantly higher percentages of slow-twitch fibers than A allele carriers (54.2 (11.1) vs 45.2 (10.2)%; P=0.003). These data indicate that 15.2% of the variation in muscle fibre composition of m. vastus lateralis can be explained by AGTR2 genotype. Next, we investigated the frequencies of the AGTR2 alleles in 2,178 Caucasian athletes and 1,220 controls. The fr