The parenteral route is the most common and effective route of administration for the drugs that have poor bioavailability and narrow therapeutic window. Recently, controlled and sustained drug delivery has become the standard in modern pharmaceutical design and an intensive research have been undertaken in achieving much better drug product with high degree of effectiveness, reliability and safety. This interest has also been sparked in parenterals; by the advantages offered by in-situ forming parenteral drug delivery systems such as ease of administration, reduced frequency of administration, decreased body dosage and thus reduced undesirable side effects, localized delivery for a site specific action, improved patient compliance and comfort. The in-situ formation of drug delivery system depends on factors like temperature modulation, pH change, presence of ions and ultraviolet radiations; from which drug get released in a sustained and controlled manner. Utilization of many biodegradable and biocompatable polymers in formulation of these systems, overcome the possibilities of adverse reactions. From manufacturing point of view even, these systems are cost effective in comparison with conventional parenteral drug delivery systems. Hence, in-situ forming parenteral drug delivery systems seems promising, as they offers a range of advantages over conventional parenteral delivery systems, and may escort to a new path in therapeutics in near future.