The aim of the present work was to formulate and evaluation injectable in situ gel matrix containing Diltiazem hydrochloride by cold method.Diltiazem hydrochloride is an anti-hypertensive agent it is rapidly and almost completely absorbed from the gastro intestinal tract but undergoes extensive first-pass hepatic metabolism. Thus oral bioavailability is only 40%. The main objective of present study is to increase the bioavailability; reducing the dose. This formulation was prepared by using thermosensitive polymer Pluronic F 127 (20%) together with carbopol 934P and HPMC. The drug polymer compatibility was studied by FTIR. The formulations were evaluated for clarity, sterility, gelation temperature, gelation time, viscosity, Syringeability, drug content and drug release. The non-irritant nature of the developed formulation was confirmed by the HET-CAM test. In vivo appearance studies were conducted on dead goat ear. The optimized formulation F6 had viscosity suitable for injecting, formulation F6 showed controlled drug release and it was found to be 80.97% up to 12 hrs. The stability studies performed on F6 showed no single change in physical appearance and drug release. It was concluded that the drug release performance was greatly affected by the polymer used in the preparation of injectable in situ gel.KEYWORDS: injectable in situ gel, Diltiazem hydrochloride, Pluronic F 127, preparation of in situ gel, evaluation of in situ gel, stability studies.