Abstract: The invention includes an improved process for producing tamsulosin comprising reacting 5-(2-aminopropyl)-2-methoxybenzenesulfonamide with 2-(o-ethoxyphenoxy)ethyl bromide in an organic phosphite solvent to obtain tamsulosin. Optically pure (R)-5-(2-aminopropyl)-2-methoxybenzenesulfonamide can be employed to produce optically pure (R)-tamsulosin product. The organic phosphite solvent utilized in the reaction can include tri-alkyl phosphites such as triethyl phosphite, trimethyl phosphite, and tributyl phosphite. Additionally, processes for producing tamsulosin having a low concentration of by-product contaminants, such as 5-((R)-2-{Bis-[2-(2-ethoxyphenoxy)ethyl]amino}-propyl)-2-methoxybenzenesulfonamide, and the use of such by-products to monitor the chemical purity of tamsulosin, are provided.