i am the NE rep for hikari, we distribute prazi pro, it does not expire for a VERY long time i.e. 5 - 10 years and even then its not "expired" its just not as strong as it was day 1. make sure to shake it very well as the praziquantel will settle. by shaking it well you can assure that the praziquantel will re-enter the oxibipropanol solution.