The purpose of this study was to develop a Interpenetrating Polymer Network (IPN) of Chitosan and Hydroxy Ethyl Cellulose (HEC). The drug Diltiazem HCl, used in the treatment of angina pectoris, hypertension and cardiac arrhythmia. Diltiazem HCl has a short elimination half-life; this will bring down its dosing frequency to once a day and on the same time make a zero order release system. Microspheres were prepared by using controlled release polymers. The formulations were evaluated for pharmacopoeial quality control tests and all the physical parameters evaluated were within the acceptable limits. Formulation B7 was proved to be good drug content, % drug encapsulation efficiency and % drug release up to 12 h as compared to the other formulations. Stability studies were carried out on the optimized formulation B7 for period of 3 months at 400c/75%RH. Finally it was observed that there was no change in physiochemical and physical properties as well as in drug release profile even after storage at 45°C and 75 % RH for three months.