The Wnt/beta -catenin pathway and p53 are very common targets for genetic alterations in colorectal cancer, and relationships between them have been reported. Here, we describe the relation between Wnt/beta -catenin signaling and the p53-related gene p73. p73, but not p53, activated a promoter containing the Tcf-binding sequence in Saos-2 cells, and the degree of activation was positively correlated with that on a p53-responsive promoter. Moreover, p73 beta enhanced Wnt/beta -catenin signaling synergistically with Wnt-3a or exogenously expressed beta -catenin, unlike p53, and the enhancement was not caused by the accumulation of beta -catenin. These results show that the effects of p73 on Wnt/beta -catenin signaling differ from those of p53.