In continuation of studies in these laboratories aiming at the bioevaluation of macromolecular anticancer drug models, in vitro cytotoxicity screens are performed on several series of water-soluble polymer-methotrexate conjugates. The methotrexate drug in these conjugates is bound through amide or ester linkages to water-soluble polyamide- or polyamidoamine-type carriers by previously developed anchoring techniques. Tests were conducted against the HeLa human cervical carcinoma cell line generally considered to be drug-sensitive, and against two variants of the rather refractory Colo 320 DM, a human colon adenocarcinoma line.