Seventy-four young bulls of the Bruna dels Pirineus beef cattle breed were reared in a typical production system and slaughtered at an average age of 381 days and live weight of 541 kg. The animals were evaluated for productive traits, carcass quality, meat quality, eating quality and biochemical characteristics of m. longissimus thoracis (LT). Biochemical measurements included intramuscular fat (IMF) and collagen proportion, haem pigment concentration, lactate dehydrogenase and isocitrate dehydrogenase activities and type I (MHC I) fibre percentage determined by ELISA. Bruna dels Pirineus bulls achieved high growth rates during the fattening period (1.63 kg/day) and showed good carcass quality, with a high dressing-out proportion (607 g/kg, hot carcass), a good conformation score (U; EUROP) and a moderate fatness score (3;1-5). Carcass composition was estimated from the sixth rib joint dissection (682 g/kg lean proportion, 127 g/kg total dissectable fat and 163 g/kg bone). IMF (24.3 g/kg) and MHC I (27.9%) showed high variabilities (CV>30%). Sensory analysis of LT included beef and livery odour and flavour intensity, and overall tenderness and juiciness assessment of loin samples (14-day ageing). Beef odour and flavour were slightly positively correlated with IMF and carcass fatness score (P<0.05). Fatness, MHC I, insoluble collagen and cooking losses tended to affect the livery flavour intensity positively. This variable was significantly higher in meat from bulls of lower carcass quality (i.e. lower conformation score, lower lean proportion; P<0.05) and higher type I fibre percentage. Loin overall tenderness and juiciness were not affected by the biochemical traits studied, however, they were negatively affected by cooking loss (P<0.05).