Introduction. The safety and effi cacy of fi nished pharmaceutical products depend on its stabilityattribute. Stability requirements were included for fi rst time in Good manufacturing practice standardMNS 5524:2014. The pharmaceutical manufacturer is responsible to conduct stability studies and tosubmit the report as part of marketing authorization documentation.Purpose of the study. The purpose of this study is to conduct ongoing stability study of the mostlyproduced domestic medicine to monitor the product over its shelf-life.Materials and Methods. As a material used 2 locally produced Paracetamol (Acetaminophen INN) 500mg tablets (local manufacturer (LM) 1 with batch number 271110, LM 2 with batch number 441110). Asa method we used shelf-life specifi cation: Mongolian national standard of Paracetamol 500 mg tablets,MNS 4358:2007. Testing frequency was at 0 time (when tablets were produced) and at 12, 24 and 36months (study was covered the shelf-life).Results. In frame of this study we defi ned the most produced product as Paracetamol (AcetaminophenINN) 500 mg tablets. From the LICEMED- medicines registration record we found 8 tablets, containingAcetaminophen in 500 mg. Two of them were produced locally. These two products were involved inongoing stability study. Testing results showed that no any stability issues over the defi ned shelf life.Discussion. The shelf life was defi ned as 36 months, initially by manufacturers before productsregistered. After a marketing authorization has been granted, the stability of the fi nished pharmaceuticalproducts should be monitored according to a continuous appropriate program that should be permittedthe detection of any stability issue associated with the formulation in the container closure system inwhich it is marketed.Conclusions. After 36 months, testing results were in acceptable limits, selected products wereremaining their quality over the shelf-life.