Carsinosine synthetase was comparatively estimated in the homogenates of chicken sternal muscle and human skeletal and heart muscles. Partially purified enzyme was obtained from chicken muscle, showing its activity of 60 nmoles carnosine/mg per min. The levels of carnosine synthesized was measured by three different methods: column chromatography on Dowen 50 x 8 resin, and thin-layer chromatography on Fixion or Silufol plates. The Silufol chromatography method was found to be sensitive and useful for measurement of the enzyme in abnormal tissues. Carnosine synthetase activity in chicken sternal muscle was compared with that published in literature. Enzymatic activities in the human skeletal and heart muscle were found to be different: carnosine synthetase from skeletal muscle was 10 times higher than that from the myocardium.