The purpose of this study was to develop a High performance liquid chromatography (HPLC) method for separating the unknown impurities generated during the accelerated stability storage of Clopidogrel Bisulphate Tablets. Also, we used the newly developed method to identify the factors that contribute to the formation of these unknown impurities in the tablet formulation. Study was carried out by incubation of mixture of excipients and Clopidogrel API in 5:1 ratio at 80°C for 3days. The new HPLC method was developed by using Kromasil 100 C18 column and using gradient method with mobile phase of 0.1% Triflouroacetic acid in water in pump A and 0.1% Trifluoroacetic acid in Acetonitrile in pump B was suitable for separating the unknown impurities from the Clopidogrel Related Compound A. The method discussed in United States Pharmacopoeia (USP) is not suitable to separate these impurities. From the excipients compatibility data we hypothesized that these unknown impurities were generated due to the excipient Polyethylene Glycol that is present in the tablet both as a tablet lubricant as well as a part of the film coating system. Further these unknown impurities were characterized as Dihydro pyridinone Derivative, Decarbmethoxylated Clopidogrel.