Thirty castrated desert sheep were used in feedlot performance and digestibility trials. Dietary treatment rations were formulated to replace groundnut cake by guar germ in a basal diet containing (%): sorghum grain, 30; groundnut hulls, 10; wheat bran, 10; molasses, 9 and common salt 1. Guar germ was included at different percentages: 0-ration A, 10-ration B, 20-ration C, 30-ration D and 40-ration E. Dry matter intake (g/kg BW) was significantly increased at inclusion of guar at levels of 20 or 30%, but significantly depressed at other levels. Digestibility of organic matter and crude protein was significantly improved by inclusion of guar at any level. That of crude fibre, however, was increased only at 30 and 40% guar levels. Disappearance of dry matter from nylon bags was almost complete within 24 h for all rations. Body weight gains increased slightly at all levels of guar inclusion in the diet. Except for the 20% level, the feed conversion ratio was also improved but this was not proved statistically. The best animal performance was obtained in response to including 30% guar in the diet.