Stability studies are pivotal necessities for ensuring safety, potency, and quality of drug products throughout their shelf-life. These guarantee that pharmaceutical products will remain stable and effective under the recommended storage conditions and are considered as prerequisite for approval of any pharmaceutical product. Stability tests are routine procedures that are conducted under different conditions for investigating the effect of variation in temperature, humidity, light intensity, and time on pharmaceutical products. Hence, these studies should be conducted and evaluated according to guidelines issued by ICH (International Conference on Harmonization) or WHO. In this chapter, we have discussed the types and methods of stability tests, storage conditions, as well as ICH and WHO guidelines.