Several TCP genes have been reported to play important roles in plant development; the TCP homologs encode a plant-specific family of putative transcription factors. To understand the evolutionary relationship of TCP genes of Arabidopsis thaliana and Oryza sativa L. (hereafter called rice), we have identified 23 and 22 TCP genes in the Arabidopsis and rice genomes, respectively. Using phylogenetic analysis, we grouped these TCP genes into three classes. In addition, the motifs outside the TCP domain further support the evolutionary relationships among these genes. The genome distribution of the TCP genes strongly supports the hypothesis that genome-wide and tandem duplication contributed to the expansion of the TCP gene family. The expression pattern of the TCP genes was analyzed further, providing useful clues about the function of these genes.