It was obvious that the most important inter-specific barrier ofthe cross between C. baccatum L. accession no. KKU-P34021 (cv. B)and C. chinense Jacq. accession no. KKU-P11176 (cv. C) occurredduring the development of the embryo. The pollen germination posed no barriers for hybridization because pollen of both cultivars was able to germinate well in the germination medium, although pollen germination was higher for those collected on the blooming day than one day before blooming and the pollen should be germinated immediately after collection. The most suitable germination medium was the one supplemented with 5% sucrose. The ‘cv.C’ pollen tended to give a slightly higher germination percentagethan ‘cv. B’. The flowering stage at which the pollen was collected(day −1 or day 0) had variable effects on the pollen tube lengthof