Brassica seeds and other oil seeds are high in protein and oil and are potentially good protein and energy supplements for ruminants. However, antinutrients present in these seeds, including glucosinolates, tannins, gossypol and others, limit their use especially in the diets of monogastric animals. Ruminants appear to be less susceptible because of rumen microbial action which may degrade some of the antinutrients. It is well known that high fat intakes by ruminants adversely affect microbial function and in a feeding experiment in which rape seed oil was incorporated in the diet of bulls, a depression in rumen fermentation and a reduction in apparent cell wall digestibility was found (Tesfa, 1993). Similarly, tropical legume seeds such as Lablab seed (Lablab purpureus), Narbon seed (Vicia narbonensis), Mungbean seed (Vigna spp.) and Cowpea seed (Vigna unguiculata) have high crude protein and low fiber contents and are likely to be valuable as concentrate feedstuffs. However, a number of antinutrients known to be present in legume seeds such as lectins, protease inhibitors, cyanogenic glycosides and amino acids such as canavanine and mimosine are considered to inhibit the growth of animals fed these seeds. In vitro degradability trials of oil seeds and legume seeds have not been carried out and there is inadequate information on the nutritive value of these seeds for ruminants. The studies reported were designed to investigate in vitro microbial degradation of dry matter of ground seeds and their influence on gas production under CBC.