When caprine butterfat was heated in the presence of water vapour and the absence of air, γ- and δ-lactones and methyl ketones were produced which were qualitatively the same as those from bovine butterfat. The saturated δ-lactone and methyl ketone potentials of the caprine butterfat were of the order of one third those of bovine butterfat when the goats and cows received similar rations. γ-Dodecanolactone, γ-dodec-cis-6-enolactone, δ-tetradec-cis-8-enolactone and δ-tetradec-trans-8-enolactone potentials of the caprine butterfat were in the same range as for bovine butterfat when the animals were on similar diets. The γ- and δ-lactone and methyl ketone potentials and the fatty acid composition of caprine butterfat varied with the diet of the goat. Supplementing the diet with polyunsaturated fat, whether or not protected against biohydrogenation in the rumen, lowered the saturated δ-lactone and methyl ketone potentials as well as the proportion of C10,12,14,16 fatty acids in the caprine butterfat. Inclusion of crushed oats in the diet increased the γ-dodecanolactone potential. The γ-dodecanolactone and they γ-dodec-cis-6-enolactone potentials were also enhanced by feeding seed oil supplements which were not protected against ruminal hydrogenation. To prevent the development of the sweet off-flavour associated with γ-dodecalactones in heated, ruminant-derived meat and butterfat with elevated levels of linoleic acid, it appears that oats should be excluded from the basal ration of the ruminant and the polyunsaturated oil supplement should have the highest possible degree of protection against biohydrogenation in the rumen.