Digestibility or diets containing cottonseed and the effect or supplementary lanolin thereon in sheep. The apparent digestibility of nutrients in four diets (A, B, C and D) containing 0, 10, 15 and 20% whole cottonseed respectively, was determined in sheep at a feeding level of 45 g DM/WO,7S /d. The apparent digestibility of dry matter (DM), organic matter (OM), crude protein (CP), crude fibre (CP), neutral detergent fibre (NDF), acid detergent fibre (ADF), nitrogen free extract (NFE) and gross energy (GE) all decreased significantly (P < 0,05) or highly significantly (P <0,01) in the cottonseed diets. This was apparently due to depressed fibre digestibility. The digestibility of the ether extract (EE) fraction, however, increased significantly (P < 0,05) and highly significantly (P < 0,01) in the cottonseed containing diets. This was probably due to the high digestibility of cottonseed oil. Nitrogen retention also increased highly significantly (P < 0,01) with increases in the whole-cottonseed content, probably due to more efficient bacterial protein synthesis (BPS). In an attempt to alleviate the negative effects of cottonseed oil on rumen metabolism, lanolin was supplemented as an emulsifier to five diets (0%, 1%, 2%,4% and 8% lanolin to diets 1,2, 3, 4 and 5, respectively). The diets contained 23 – 25% whole cottonseed. The apparent digestibility of nutrients was determined by feeding the diets to five groups of wethers (four per group) at 45 g DM /W0.75 / d. Because of the promising results obtained with the 2% lanolin inclusion, the work was repeated with Rations 1 and 3 (with 0 and 2% lanolin respectively) using 10 wethers per group. The apparent digestibilities of the NDF (ONDF) and the nitrogen (DN) were significantly (P < 0,05) and highly significantly (P < 0,01) higher for Ration 3 (2% lanolin) than for Ration 1 (0% lanolin). The small increase in the total digestibility of nutrients with the inclusion of 2% lanolin, seems too small to justify its inclusion in diets containing high percentages of whole cottonseed.