Reliable and affordable supplies of health commodities are critical for the success of the healthrnsector. This is particularly very important when it comes to infectious diseases such asrnTuberculosis (TB) where sustainable availability of drugs play an important role in halting therndisease progression and development of resistant strains of the causative agent. The objective ofrnthe study was to identify determinants of stock outs of first line anti TB drugs at public healthrnfacilities under Addis Ababa City Administration Health Bureau. Both descriptive and explanatoryrnresearch design with mixed approach involving both quantitative and qualitative data collection,rnanalysis and interpretation was employed. Quantitative data was collected from drug storernmanagers of health facilities providing TB treatment and qualitative data from Addis Ababa hubsrnof the Ethiopian Pharmaceuticals Supply Agency (EPSA), Addis Ababa City Administration HealthrnBureau and selected heads of pharmacy departments of health facilities. More than half of thernhealth facilities encountered stock out for at least one of first line anti TB drugs with the period ofrnprevious one-year to the date of the visit. Significant level of stock out was observed in pediatricsrnformulations with 39.8% of health facilities stocked out for RH 75/50 mg and 16.9% for RHZrn75/50 mg and the stock out level for Ethambutol 100 mg & Isoniazid 100 mg also calls for muchrnattention. Regression analysis showed poor performance of supplier (EPSA) is the significantrndeterminant for stock out of first line anti TB drugs at 95% level of confidence (p=0.00). Thernproblem with pediatrics formulation is persisting, the reason mainly being negligence by healthrnfacilities in not placing early orders since pediatrics cases only arrive intermittently, hencernthought as these cases are not available. Poor performance by the supplying hub (delay in supply,rninadequate supply, and stock outs there) was found to be the main determinant for stock outs .Thisrncalls for collaboration among stakeholders working especially on Tuberculosis andrnpharmaceuticals supply in preventing stock outs for anti TB drugs and to strengthen the drugrnsupply system in general.rnKeywords: Stock out, Anti TB Drugs, Information Communication Technologies, Health SystemrnSupport, Performance of the Supplying Hub, Public Health Facilities, Addis Ababa