The formulation of pseudoephedrine Hydrochloride (HCl) extended release was prepared by using different polymers (HPMC and ethocel) and with different diluents (dibasic calcium phosphate anhydrous, dibasic calcium phosphate dihydrate, lactose anhydrous and DCL-15). The experimental work including preformulation studies, formulation development and evaluation. The results of the present study point out that the type and level of excipients influence the rate and extent of pseudoephedrine HCL extended release. The insoluble diluents especially dibasic calcium phosphate causes that the drug to be release at a slower rate and to lesser extent than the soluble diluents (lactose) was investigated. The effect of pseudo polymorphic form of dibasic calcium phosphate on the dissolution profile was studied. Analysis of dissolution profile on the basis of Higuchi’s model suggested that the drug release mechanism basically swelling and diffusion controlled.