The development of harmonised data requirements for microbial pesticides has been a goal of the OECD for several years. A guidance for registration requirements would facilitate access to a wider range of new, reduced risk, IPM compatible pest management tools, by making it easier for companies to submit registration applications to many countries and for regulatory agencies to benefit from each other’s reviews. This document proposes guidance for registration requirements for microbial plant protection products, as well as indicating where there are differences among countries.