To determine and to compare the ruminal crude protein (CP) degradability of some sub-tropical protein sources, chickling vetch (Lathyrus sativum), bitter vetch (Vicia ervilla), lentil screenings, fish meal (FM), corn gluten meal (CGM), soybean meal (SBM), formaldehyde treated soybean meal (FT-SBM), four cannulated yearling Awassi male lambs were used. Crude protein of chickling vetch, bitter vetch and lentil screening were degraded more rapidly and more than 70% of FT-SBM and CGM crude protein remained undegraded even after 24 hours incubation. Formaldehyde treatment decreased CP degradability of SBM (P<0.05). It is concluded that legume seeds tested lit this study are primary sources for rapidly degradable protein in the rumen. It is also concluded that formaldehyde treatment may have a potential to decrease rumen degradability of high quality vegetable protein sources.