Parenteral delivery provides rapid onset even for the drug with narrow therapeutic window, but to maintain the systemic drug level repeated installation are required which cause the discomfort. Therefore, a delivery system that combines the simplicity and reliability of solid implant devices along with convenience and ease of administration on of micro-particles are desired. In situ gel forming system represents a desired alternate. The atrigel system is a proprietary delivery system that can be used for both parenteral and site specific drug delivery. it consist of biodegradable polymers dissolved in a biocompatible carriers when the liquid polymer system is placed in the body using standard needles and syringes, it solidifies upon contact with aqueous body fluids to form a solid implant. There are some advantages of these system are compatibility with a broad range of pharmaceutical compound, less invasive technique, direct delivery to a target area, protection of drug, sustained drug release, few type of atrigel are surgical implants, microspheres, liposomes and injectable gels.