Used were 15 bulls and 15 heifers of the Black-and-White Polish Holstein-Friesian breed, semiintensively fattened, with the aim of evaluating the effect of sex on the selected traits of quality of beef. Bulls were slaughtered at the mean age of 536.2 days and 523.1 kg body weight, and heifers at 528.7 days and 459.7 kg body weight, respectively. After slaughter and post-slaughter treatment, the carcasses were graded according to the EUROP system. Meat quality was assessed based on pH, colour, chemical composition (including fatty acid profile), and sensory and histological properties. The results obtained show that quality of beef in terms of technological properties and chemical composition, especially fatty acid profile, is higher in heifers than in bulls.