The study was conducted to evaluate the chemical composition and fatty acid profile of the Longissimus dorsi muscle of fi rst (PUR1) and second (PUR2) generations of Purunã-breed cattle, and compare them to their ancestral generations (PUR). Thirty-nine young bulls with an average initial weight of 236 kg and initial age of 10 months were used. The animals were slaughtered at the age of 16 months with an average final weight of 464 kg. The content of water, ash, crude protein and total cholesterol in the muscles were similar (P>0.05) among the different genetic groups. The levels of total intramuscular fat were higher (P<0.05) for PUR in comparison to PUR1 and PUR 2. The percentage shares of 14:0, 14:1 n-7 and 16:0 fatty acids were higher (P<0.05) as a percentage of total fatty acids in PUR2 and PUR in comparison to PUR1. Thus, the 22:6 n-6 ratios were greatest (P<0.05) for the PUR1 genetic group. The lowest (P<0.05) percentage was observed in PUR. There were no difference (P>0.05) in SFA, MUFA, PUFA, n-3, or in the PUFA:SFA and n-6:n-3 ratios, when comparing the fi rst and second Purunã generations to their ancestors.