Mitochondrial DNA (mtDNA) from 40 samples of the Taipei treefrog Rhacophorus taipeianus collected from seven populations in Taiwan were sequenced to document the DNA sequence variation in anuran mtDNA and to elucidate the phylogeographic population structure in the Taipei treefrog. Sequences of 722-764 bases in length, including a 108-bp segment of the cytochrome b gene and a 614-656-bp D-loop segment, were obtained by direct sequencing using polymerase chain reaction (PCR). The variation in length was due to a 40-bp region that tandemly repeated four to five times in the D-loop region. The first repeat is the most conserved one among the five repeats because there are no variable sites in this repeat. Besides the 40-bp length variation, 28 positions in the 764-bp sequences are variable and distributed evenly in the cytochrome b gene fragment and D-loop region. Variation in the D-loop of the Taipei treefrog is comparable to those of other vertebrates. Two well-differentiated lineages (northern and central) differing by mean sequence divergence of 1.7% are identified and concordant with their geographic distributions. The two lineages are inferred to have split from a common ancestral population in the early Pleistocene. However, the interpopulation divergence of the northern lineage (< 0.33%) is apparently lower than that of the central lineage (1.11%), implying that the two lineages evolved independently and had different demographic histories after divergence. This study reveals that anuran D-loop has potential as a genetic marker in phylogenetic and population genetic analyses of anurans.