Five digestibility trials were carried out to investigate the effect of different roughage sources on feed and water intakes, water metabolism, nutrient digestibility coefficients, nitrogen utilization and some rumen fluid parameters. Twenty mature male Ossimi sheep were randomly assigned to five experimental groups (four animals in each treatment). Animals were fed on 3% DM of live body weight and received one of the following diets. All the experimental diets contained 50% concentrate feed mixture (CFM) plus 50% roughage. Control diet contained berseem hay (BH), while the other four experimental diets were replaced BH in control diet by peanut vein hay (PVH); beans straw (BS); kidney beans straw (KBS) or linseed straw (LS). Results showed that, source of roughage were affected on the chemical composition of the experimental diets. Diet contained BH showed the highest value of CP (15.69%), followed by PVH and LS diets (14.52 and 14.23%, respectively. On the other hand CP content of BS and KBS diets were in the same range (12.65 and 12.42%). Beans straw recorded the highest value of neutral detergent fiber (53.16%), acid detergent fiber (37.84%) and cellulose contents (28.30%), however, PVH diet showed the lowest value of ADL (7.30%). Inclusion PVH, BS, KBS and LS in sheep diet significantly increased (P<0.05) feed consumption as DM, TDN, CP and DCP intakes compared to the BH containing diet. Sheep received BS diet significantly increased (P<0.05) drinking water (4650 ml/h/day), total water intake (4829 ml/h/day) compared to the other diets. Inclusion different sources of roughage in sheep diet had no significant effect on DM digestibility. While, sheep received KBS diet significantly (P<0.05) increased OM, CP and CF digestibilities compared to the other different diets. Introduce PVH, BS, KBS and LS in sheep diets significantly decreased (P<0.05) total digestible nutrient and digestible crude protein values compared to the control diet. All groups were positive nitrogen balance and sheep received LS diet recorded the highest values of nitrogen retention (21.7 g) and nitrogen retention % of digested nitrogen (81.61%) compared to the other diets. Dietary treatments significant affected (P<0.05) on pH value, ammonia nitrogen (NH3-N) and total volatile fatty acids (TVFA's) concentrations. Three hrs post feeding significantly (P<0.05) decreased ruminal pH value, while, it significantly (P<0.05) increased both ruminal NH3-N and TVFA's concentrations. It could be concluded that we can using alternative sources of roughage successfully in sheep diets as a good sources of roughages instead of berseem hay with better feed intake, digestion coefficient, nitrogen utilization and ruminal fermentation. Also we can use the tested materials to formulate cheap diets for sheep. [Hamed A.A. Omer, Mohamed A. Tawila and Sawsan M. Gad. Feed and Water Consumptions, Digestion Coefficients, Nitrogen Balance and Some Rumen Fluid Parameters of Ossimi Sheep Fed Diets Containing Different Sources of Roughages. Life Sci J 2012;9(3):805-816]. (ISSN: 1097-8135). http://www.lifesciencesite.com. 115