sRNA were extracted from postmitochondrial fraction of rat sceletal muscles by the phenol method. Their yield, physico-chemical properties and acceptor activity during postmortal destruction were studied. Within 2 days after the death yield of sRNA was decreased by 18-20% with maintenance of the physico-chemical properties studied. At the same time the acceptor activity (towards 4 amino acids) was distinctly decreased. For various amino acids correlation between a decrease in the acceptor activity and the time of autolysis was different. Three peaks of radioactivity were observed when 14C-phenyl-alanine-sRNA was fractionated on DEAE-Sephadex A-25; two of them were distinctly decreased after 24 hrs autolysis but the third one was maintained almost without alterations. The data obtained suggest that separate types of sRNA are degraded selectively at early steps of postmortal autolysis.