SK3530·2HCl, (2-(5-(4-(2-hydroxyethyl)piperazin-1-ylsulfonyl)-2-n-propoxyphenyl)-5-ethyl-7-n-propyl-3,5-dihydro-4H-pyrrolo[3,2-d]pyrimidin-4-one dihydrochloride), is a novel a new phosphodiesterase type V (PDE V) inhibiting agents. The pharmaceutical development of SK3530 necessitated the availability of an assay for the quantification and purity determination of SK3530 active pharmaceutical ingredient (API) and its pharmaceutical dosage form. A reversed-phase high performance liquid chromatographic (HPLC) method with ultraviolet (UV) detection was developed, consisting of separation on a C18 column with a CapcellPack MG (4.6 mm × 150 mm, 5 μm) column with ammonium acetate buffer (pH 4.0, 20 mM)–acetonitrile (60:40, v/v) as the isocratic mobile phase and UV detection at 250 nm. The method has been shown good chromatographic separation for SK3530 and the other related substances. The method was found to be linear 200–300 μg/ml, precise and accurate. Stress testing showed degradation products, which were well separated from the parent compound, confirming its stability-indication capacity. Moreover, the use of LC–MS and on-line diode array detection enabled us to propose structures for degradation products.