Recombinant plasmids have been isolated which contain sequences complementary to two distinct alpha-tropomyosin mRNA species present in chicken leg muscle. The proteins coded for by these different mRNAs could be distinguished by their electrophoretic behaviour in the presence of 3.5 M urea. The properties of the minor alpha-tropomyosin of chicken leg muscle were similar to those reported for the alpha-tropomyosin of slow twitch chicken skeletal muscle. Sequence analysis of available plasmids showed that the deduced protein sequences of both types of alpha-tropomyosin were very similar and closely related to the known protein sequence of rabbit alpha-tropomyosin. However considerable variation in nucleotide coding sequence of the two alpha-tropomyosin mRNAs was found.