It was obvious that the most important inter-specific barrier of the cross between C. baccatum L. accession no. KKU-P34021 (cv. B)and C. chinense Jacq. accession no. KKU-P11176 (cv. C) occurred during 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 percentage than ‘cv. B’. The flowering stage at which the pollen was collected(day −1 or day 0) had variable effects on the pollen tube length of ‘cv. C’, but for ‘cv. B’ the pollen collected on day 0 in most cases could grow a longer pollen tube than those collected on day −1. The germination medium supplemented with 5% sucrose also induced the best pollen tube growth for ‘cv. C’ in addition to giving the high-est percent germination. It is well-established that sucrose is the most common energy source utilized during pollen germinationand pollen tube growth for synthesis of cell wall materials including pectins, cellulose and callose (Mascarenhas, 1993) and optimum sucrose concentrations for different plant species varied greatly.Similar to this study, Mercado et al. (1994) found that pepper pollen (C. annuum L.) required relatively low sucrose concentration(5–10%) for germination and gave rise to comparable maximum percentage of pollen germination. However, media with sucrose concentration higher than 30% gave the low pollen germination and pollen tube growth due to their imbalance between water and sugar, and resulted in loss of pollen germination (Chaengkrachanget al., 2006; Mascaren has and Bell, 1969). It appeared that pollen of ‘cv. C’ could develop as much as 2–3 times longer pollen tubes than ‘cv. B’ under most conditions tested. The genotypic differencein pollen germination and pollen tube growth could be due to thevariation in their pollen carbohydrate concentration (Pacini, 1996).The information on factors affecting pollen germination and tube growth of C. chinense and C. baccatum in this study could be useful for preparing the good quality pollen in producing the hybrid seeds between these two species.