Alternative splicing of pre-mRNAs is a major mechanism of generating protein diversity in higher eukaryotes. It is well known that one of the major forms of alternative splicing is exon skipping, which alternatively skips specific exon during splicing. Previous research, by Miriami and his colleagues, was conducted by using a statistical method to identify two motifs both in upstream and downstream introns that were associated with exon skipping events. In this study, we employed pattern branching motif finding algorithm and approximate mining of consensus sequences algorithm. The data mining approach developed in the study showed its strength of being able to completely discover all possible motifs and made itself a more ideal approach compared to Miriami?s.. statistical one. Furthermore, because of the similarities in genes between human and mouse, we compared the two species? motifs in our study. We also discovered the patterns are very likely associated with exon skipping event between human and mouse.