Thirty hams were allotted into four groups according to fattening diet ("Montanera"-acorns and pasture; and "Pienso"-concentrated diet) and genotype of pigs (Iberian and Iberian x Duroc pigs). Total lipids, triacylglycerol composition and fatty acids from neutral lipids fraction were measured in biceps femoris muscle. Fattening diet largely affected lipid composition of hams. Total intramuscular lipids and triacylglycerols content were higher in Montanera hams than in Pienso hams. In Montanera hams, triacylglycerols contained more oleic acid (C18:1) and less stearic (08:0) and palmitic (C16:0) acids (p < 0.001) and accordingly less PSO, PPL, PPO, PPS, SSO (p < 0.001) and more OLL, OOL, 000 triacylglycerols compared to Pienso hams (p < 0.001). Genotype of pigs has an important effect in triacylglycerols composition but only a limited effect on their fatty acids composition. So, Iberian hams contained more of PLLn, PLL, POLn and POL + SLL compared to Iberian x Duroc hams (p < 0.001) and POO and SOO were present in a higher quantity in Iberian x Duroc hams (p < 0.01). (C) 2004 Elsevier Ltd. All rights reserved.