'Takasago (Rockport Bigarreau)', one of the major early ripening cultivars of sweet cherry in Japan, was reported to be cross-incompatible with 'Hinode (Early Purple)'. Thus, they were assumed to have the same S- alleles, although their S-genotypes were unknown. However, when 'Takasago' was cross-pollinated with 'Hinode' at the Yamagata Prefectural Horticultural Experiment Station, the fruit set normally (unpublished data), which suggests that they are cross-compatible. In this study, we re-evaluated crossability between the two cultivars by controlled pollination tests and determined their S-genotypes by the molecular typing system recently developed for S-alleles of sweet cherry. The cross-pollination tests conducted at two different locations in Japan showed that 'Takasago' and 'Hinode' were self- incompatible but reciprocally cross- compatible. Furthermore, 2D-PAGE (two dimentional- polyacrylamide gel electrophoresis) analysis for stylar extracts revealed that they have none of the common S-RNases, S-gene products in styles of sweet cherry, which suggests that their S-genotypes are completely different. By S-RNase spot patterns in 2D-PAGE profiles and RFLP (restriction fragment length polymorphism) analysis, S-genotypes of 'Takasago' and 'Hinode' were proposed to be S-1 S-6 and S S-2(x) (S-x is a novel S-allele different from S-1 to S-6), respectively. This implies that 'Hinode' is cross- compatible with all cultivars of known S-genotypes. The usefulness of biochemical and molecular methods for S- allele typing employed in this study is discussed.