This document provides guidance to both industry and regulatory authorities in the context of the assessment of technical equivalence of micro-organisms used in plant protection products. This Guidance Document is applicable for changes to the same strain of micro-organisms only in the framework of application for authorisations for plant protection products, where the strain already has been approved. The evaluation involves comparison between two sources of technical active ingredient of the same strain of a micro-organism for several parameters, aiming to ensure that the new source is equivalent to the approved source.