Studies were carried out both on the quantitative and qualitative composition of aminoacids in the proteins of n. longissimus dorsi, from sheep of the "Blackheaded Pleven" breed. For the purpose was used an automatic aminoanalyzer of 1200 E, made in Czechoslovakia. Hydroxyproline and triptophane were determined in separate analytical pathways. It was established that in the proteins of the muscle investigated are contained the following aminoacids, expressed in grams /16 g N: lysine--7,90; treonine--3,92; valine--4,84; methyonine--2,72; isoleucine--4,51; leucine--7,54; phenylalanine--4,64; triptophane--1,39; histidine--3,02; arginine--6,09; aspartic acid--7,16; serine--3,64; glutamine acid--11,49; proline--3,54; glycine--4,29; alanine--4,65; tirosine--2,94 and hydoxyproline--0,42. A similarity was proved in the aminoacid composition of m. longissimus dorsi from sheep with that of the same muscle with cattle and swine.