Sweet lupines are presently being cultivated at the Experimental Station in Gorbea (Chile). Four cultivars, Lupinus albus cv Astra, L. albus cv Multolupa, Lupinus luteus cv Aurea and Lupinus angustifolius, were examined for the chemical composition of whole and dehulled seeds and testa. Whole seeds contain 34-35% protein. The varieties of L. albus contain 13% oil. L. luteus and L. angustifolius contain about 5% ether extract. Crude fiber ranged from 11 to 17% in the whole seed. Unsaturated fatty acids, especially oleic and linoleic, make up about 80% of total fatty acids. The alkaloid content of the seed was 0.02%. The amino acid composition of the protein indicated that the main deficiency corresponds to the sulfur-containing amino acids, i.e. methionine + cystine. The protein efficiency ratio values for L. albus cv Multolupa was 1.08 and 2.50 for casein. Supplementation with DL-methionine at 0.1, 0.2, 0.3 and 0.4% of the diet significantly increased the basal value from 1.08 to 2.14, for the supplemented diet with 0.1% (p less than 0.01). Higher levels of supplementation did not cause significant increases in the protein efficiency ratio. Apparent protein digestibility for the rat was 75% for unsupplemented lupine. This value increased to about 79% (p less than 0.01) for the supplemented diets (casein 88.7%).