Sweet cherries (Prunus avium L.) are generally self-incompatible and pollinator cultivars are needed in orchards for reliable yield. In Hungary, choosing the appropriate cross-compatible cultivar pairs has so far been based on traditional test-crosses in the field. In recent years PCR-based methods that allow the identification of the S-alleles responsible for compatibility have been elaborated. We have determined the S-allele constitution of 24 cultivars and four selections important to Hungarian growers and breeders using PCR-based methods developed at Horticulture Research International, East Malling. The 28 accessions had various pairs of 9 alleles including one new allele, S_r. They could be assigned to 12 of the existing incompatibility groups or to a new group (S₄S₁₂) for which the designation 'Group XXVII' is proposed. The cultivars `Krupnoplodnaja' and 'Rita' had novel genotypes, S<sub>5</sub>S<sub>9</sub> and S<sub>5</sub>S<sub>x</sub>, respectively and can be placed into group 0 that holds universal pollen donors. The genotype of the cultivar ‘Hedelfingeni óriás' grown in Hungary was found to be S<sub>3</sub>S<sub>4</sub> and therefore different from the cultivar `Hedelfingen' that is widespread in Western Europe.