The experiment examined the effect of breed, diet and sex on pig performance and carcass quality. Eight sires of the Duroc and Large White breeds each produced four experimental litters. Two boar and two female pigs from each litter were reared under standard conditions to 38 kg and then one of each sex was allocated to each of two finishing diets. These were cereal-based diets with and without 16 g/kg soya oil. Following slaughter at 80 kg, loin chops taken from half of the pigs (two litters per sire) were subjected to detailed investigation of physical, chemical and organoleptic characteristics. Lifetime live-weight gain was similar for both breeds but Duroc-sired pigs had greater voluntary food intakes and poorer food conversion efficiencies in the finishing stage. They also had greater killing-out proportions (775 v. 755 g/kg, P < 0·001) and backfat thickness at slaughter (284 v. 27·2 mm at P1 + P3, P < 0·05). Fat firmness measured by penetrometer at 4°C was lower in Duroc-sired pigs (738 v. 792 units, P < 0·001). The proportion of extractable intramuscular lipid was greater in chops from Duroc-sired pigs (13·8 v. 10·4 g/kg, P < 0·001). There were no significant effects of breed or diet on the eating quality of the grilled chops as assessed by a trained taste panel and a consumer panel.