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In this study, 72 Varamini male lambs at seven months of age with an average body weight of 38.4±19 Kg were randomly divided into 9 groups (8 lambs/group) . The lambs were fed with nine different rations which were supplemented with sulfur(S) and contained urea-treated straw (UTS):
(0)S,(0)UTS; (0.1)S.(O)UTS; (0.2)S,(0)UTS; (0)S,(15)UTS;(0.1)S, (15)UTS;(0.2)S,(15)UTS;(0) S, (30)UTS;(0.1)S, (30)UTS and (0.2)S,(30)UTS, respectively for 100 day. The ratio of nitrogen to sulfur(T) in the rations which had 0, 0.1 and 0.2 , of S was 10, 6.6 and 4.9, respectively. The diets were isocaloric and isonitrogenous . After a 30 - day adaptation period the lambs were drenched and vaccinated and were fed for 100 days .The parameters which were measured included diameter(mm), staple length(cm),medulation(%) , type of fibre(%) , vegetable matter(%), wool nitrogen(%), wool sulfur(%) and clean wool(%).Mean fibre diameter was significantly (P <0.05) different among groups of lambs which recieved different level of S supplement . The lambs which were fed with the ration containing 0.2% S, had lower wool diameter, while, the group which recieved the rations without S had a higher number of fibres greater than 60(mm) diameter. Clean.wool, coarse and fibre length percentages of the lambs which recieved 15% UTS were significantly. (P<0.05) different ,from other treatments. The wool quality of lambs that did not recieve S, UTS or both, was low. Incorporation of S or LJTS did not significantly alter wool nitrogen, but significantly (P<0.01) changed wool sulfur content. The lambs which received the highest level of S and UTS (0.2 and 30% respectively) had optimum wool length and uniform fibre length , diameter, clean wool and fleece weight