The antitumor alkaloid 11-hydroxy-(20S)-camptothecin was isolated from the woody tissue of Camptotheca acuminata. Structural proof derived from comparison with racemic 4 prepared by total synthesis. Antitumor activity of racemic 4 in L1210 leukemia in mice was considerably greater than that of natural (20S)-camptothecin and its sodium salt. There was also no toxic effect observed even at relatively high doses.