Phytopathogenic fungus Cryphonectria parasitica is the causal agent of chestnut blight in the European chestnut Castanea sativa Miller. This fungus is also the natural host of the virus Cryphonectria hypovirus 1 (CHV-1), which reduces fungal virulence and sporulation ability. Hypovirus can spread only between fungal strains that belong to the same vegetative compatibility (VC) type, i.e. that contain identical alleles at all vic loci, and less frequently from the strains in which there's a a difference in only one of six loci which determine the diversity of VC types in Europe. In this research C. parasitica populations from Ozalj and Kašt area were analyzed. The aim was to determine the diversity of VC types and the percentage of hypovirulent isolates with white morphology. In Ozalj population the dominant VC type was EU2 which represented 34% of the total number of isolates, followed by EU1 which represented 19% of the total number of isolates. The prevalence of VC types EU14, EU39 and EU40 was 4% each. The VC type of 35% of isolates from Ozalj could not have been determined, they were incompatible with all of the known VC types. In Kašt population the most common type was EU1 (32% prevalence), followed by EU17 with (16% prevalence). EU2 and EU40 appeared less frequently (each with 12% prevalence) as well as EU3, EU5 and EU12 (each with 4%). Undetermined isolates constituted 16% of the studied Kašt population. Vegetative diversity was high and the presence of hypovirus was relatively low, up to 30%, which makes natural biological control difficult.