A new family of water soluble camptothecin derivatives is described. Their synthesis, in vitro cytotoxicity, and in vivo antitumor activity is reported. Compounds 5a and 5e displayed excellent in vivo antitumor activity both ip and iv.Camptothecin (1), firstly isolated by Wani and Wall from Camptotheca Acuminata, 2 is a potent inhibitor of DNA topoisomerase I. 3 Some of its derivatives 4 are being tested clinically as anticancer drugs in Europe, USA and Japan. Among them 9-amino camptothecin 5 (9-AC, 2) has emerged as one of the most promising clinical candidates for cancer treatment. Nevertheless its water insolubility and the difficulties associated with the synthesis of multigram quantities have retarded its clinical development until recently: Now we wish to report our preliminary results on the synthesis and antitumor activity of a new series of water-soluble amino camptothecin derivatives, amidino camptothecins (5), endowed with high in vitro cytotoxicity and good in vivo activity.