Dating, pollen, and charcoal particle findings are presented from two mangrove swamp cores recovered from Pohnpei, Eastern Caroline Islands, Micronesia. The cores, from opposite sides of the island, provide continuous sediment sequences dating from the early Holocene. Pollen analysis demonstrates that the giant swamp taro (Cyrtosperma chamissonis), an important cultigen on many islands in the Western Pacific, was growing on Pohnpei during prehuman times, indicating that its natural prehuman distribution was far wider than previously suspected. The archaeological implications for the prehuman presence of C. chamissonis are discussed. The cores are inconclusive with regard to the timing of initial human settlement and landscape change on Pohnpei, possibly due to their location deep within large coastal mangrove forests where terrestrial pollen types and charcoal from local fires are poorly dispersed