Lamb is characterized as having a low ratio of polyunsaturated (PUFA) to saturated fatty acids (P:S ratio) of approximately 0.1-0.2; considerably less than the minimum recommended ratio of 0.45 for the human diet as a whole (Department of Health 1994). Offset against this, lamb has a favourable ratio of the beneficial PUFA of the n -3 series with the n -6/n -3 ratio being well within the recommended value of < 4.0, and is a particularly rich source of the longer chain n -3 PUFA. One of the major obstacles to improving the P:S ratio of lamb is the extensive biohydrogenation of PUFA in the rumen, resulting in some form of protection being required. The objective of the current experiment was to manipulate the P:S ratio in lamb, whilst maintaining the n- 6/n -3 ratio, through feeding protected fat sources.