Technical Abstract: Artificial cross-pollinations were carried out among six species of Celtis (C. bungeana, C. koraiensis, C. laevigata, C. occidentalis, C. reticulata, and C. sinensis) in order to test the potential for interspecific hybridization in Celtis breeding. AFLP profiles were used to assess the ancestry of progeny. Hybrids were formed very rarely among these six species of Celtis: only two interspecific hybrids were obtained. Self-pollination occurred occasionally in non-emasculated trees. AFLP analysis yielded false paternal markers at a very low frequency, likely due to DNA methylation differences. Plants with unexpected paternal markers were confidently distinguished from hybrids by calculating the probability of obtaining the observed number of paternal markers by chance. The study showed that species of Celtis do not hybridize as readily as previously thought, and interspecific hybridization may not be the best approach for introducing superior Celtis cultivars. The study also clearly demonstrated the importance of using large numbers of markers in assessing paternity of hybrids.