Self-incompatibility of apricot (Prunus armeniaca) is governed by the multiallelic S-locus, in which the pistil S-ribonuclease (S-RNase) and the pollen expressed Shaplotype specific F-box (SFB) genes reside. In apricot, self-compatibility (SC) is due to a loss-of-function mutation within the pollen gene of the SC-haplotype. Apricot S8-, S9- and S C-haplotypes were analysed using fruit set evaluation, genomic PCRs, RTPCRs and DNA sequencing of the S-RNase and SFB alleles. Controlled pollinations revealed that the cross 'Ceglédi óriás' (S8S9) × 'Ceglédi arany' (SCS 9) set well, but the reciprocal cross did not. Sequence analysis revealed that SFB8 is the first known progenitor allele of a naturally occurring SC allele in Prunus. A phylogenetic analysis suggests that SC-haplotype could have evolved in a cultivar with S 8Si genotype, where Si is an unidentified incompatibility allele. The SCS8 Magyarkajszi cultivars might have developed from such a mating. Several single nucleotide polymorphisms were identified in the SC-RNase and could be used for monitoring apricot dissemination routes between Eastern and Western Europe. The apricot SC-RNase was subjected to an intron phase analysis revealing some protein evolutionary aspects. Our results have notable implications for the elucidation of the evolutionary history of present day apricot cultivars and, in general, for the understanding of the transition from selfincompatibility (SI) to self-compatibility.