The objective of this study was to investigate the polar and neutral lipid fatty acid composition of pig muscle as influenced by rearing conditions and sex. A total of 120 Hampshire crossbreeds were divided in two groups, one reared free-range in a strip grazing fashion and one reared indoors in a large pen (120 m(2)). Free-range rearing produced a more unsaturated fatty acid composition (M. biceps femoris) in the neutral lipids, although the effect was small. In the polar lipids the effect of rearing condition was sex dependent. In the muscle of free-range gilts, there was a higher level of C18:2 n-6, compared with indoor gilts, indoor castrates, and free-range castrates. Moreover, muscle of gilts irrespective of rearing condition, had a higher level of the C⩾20 polyunsaturated fatty acids in the polar lipids (16.75 and 14.60, respectively). Thus, we suggest that the difference between castrates and gilts with respect to fatty acid composition in the polar lipids, might be affected by rearing condition.