During the development of walnut (Juglans regia L.) male sexual system the most frequently noticed anomalies there are conditioned by low temperatures (-10–150C) in the meiotic period (the end of March – fi rst half of April months). As a rule in the exterior part of infl orescences of protandrous as well as of some protoginous genotypes microsporogenesis is lead rapidly. In the microspores mother cells appear big vacuoles, pushing slowly hypertrophied nucleus to tapetal tissue. There are observed typical phenomenon of cytomixis and picnosis with passage of fragments of nucleus and nucleols from one cell to another. Tapetal tissue is aff ected too, but there could be founded some sectors with normal development.