The effect of temperature and duration of storage on the potency of trivalent oral polio vaccine (Sabin type) were investigated. Temperature was set up at the beginning from : —20 C, 0 C, 5 C, 10 C, 15°C, 25 C and 30°C. During 30 days period of storage, the polio virus was titrated at 4 days interval using micromethod of TCID5 0 calculation in Vero cells. The result of the study showed that the effect of -20°C, 0°C and 5°C for 30 days of storage was not significantly different. Whereas at 10°C the vaccine potency had started to decrease at day 24 up to day 30. At 15°C the potency had started to decrease at day 12, while at 25°C and 30°C the potency of vaccine drooed sharply at day 4 of storage.