The aim of this research was to formulate and evaluate in-situ liquid depot from bio-degradable polymers like PLGA 85:15 and PLGA 50:50.Isoniazid is a drug of choice for the treatment of tuberclosis. It requires prolong therapy, it has very short half life (Fast acetylators) of 1.1 + 0.1 to 2-3 hrs. Isoniazid is readily absorbed orally and penetrates all body tissues; it is extensively metabolized in liver, most important pathway being acetylation metabolites are excreted in urine. The developed Isoniazid Insitu liquid depot was characterized for percent drug content (PDC), drug polymer interaction study, viscosity, and drug release study. The results of the study showed there were no interaction in drug and polymers after formulation, viscosity was found in all formulation between 1.02 to 1.57 poise and drug content was found to be very between 92.39 + 0.47% to 97.15 + 0.31%. It was found that the amount of drug released at after 168 hours was greater from PLGA 85:15 depots systems formulations as compared to PLGA 50:50 biodegradable liquid depot injections. The results of the characterization and evaluation of in-situ liquid depot established the safety for use and suitability.