Twenty-three andesites from the Tatun Volcano Group, northern Taiwan, were analyzed for Si, Ti, Al, Fe, Mg, Ca, Na, K, Rb, Ba, Cs, Hf, Th, Sc, Co, and seven REE. Five types of andesite are distinguished in terms of mafic minerals, major elements, and some trace elements. The average Tatun andesite has similar Si, Fe, Al and Mg content, but lower Ti and Na and higher K and Ca content, than those of average circum-Pacific andesite. The average chondrite-normalized REE distribution patterns of the five types of Tatun andesites are quite similar, showing enrichment in light REE, a slight negative Eu anomaly, and approximately chondritic proportions in heavy REE. These are similar to Iwo-Jima andesite, but differ from Bougainville low-Si andesite. The average Tatun andesite has lower Mg and Ni content than high-alumina basalt found in the Tatun volcanoes, and has higher Rb and Th, and lower Co, than average Formosan basalt. The 07Sr/ 06Sr ratio (0.7040) in Tatun andesite is similar to oceanic island basalt, and indicates very little sediment and crustal contamination. Ultramafic inclusions, appearing as amphibole-rich nodules, are also found in Tatun andesites; they consist of amphibole and Ca-rich plagioclase (An 95). These data and criteria suggest that the Tatun andesites most likely originated from fractional crystallization of a parent basaltic magma enriched in water.