Oral polio vaccine (OPV) proved to be superior in administration eliminating the need of sterile syringes and making the vaccine more suitable for mass vaccination campaigns. Poliovirus is heat sensitive in nature, and thus OPV is stored at low temperature (frozen). The growth medium containing varying concentration of serum such as 6, 8, 10, 12, 14% were prepared. 10 ml of the above mentioned growth media containing different concentration of serum were added to different culture bottles. The culture flasks containing different volumes of growth medium with 10% serum concentration such as 8, 9, 10, 11 and 12 ml were added to a series of culture flasks. All the culture flasks were inoculated with the RD cells (10,000 cells/culture flask) and kept at 37°C. The most favoured serum concentration and volume for the growth of RD cells was found and used for testing the potency of vaccine. Vaccines from two manufacturers were kept at three different temperatures, 2-8 ± 0.5°C (refrigerator), 26 ± 0.5°C and 37 ± 0.5°C (Incubator). Cytopathic viruses were titrated by the determination of a tissue culture infectious dose 50 (TCID 50 ), vaccine dilutions were seeded in replicate onto cells in multiwell plates (usually 96 wells). After a suitable incubation period, wells were examined microscopically and scored as infected or not infected. The potency of vaccines was tested using the Karber's Formula.