A pharmaceutical composition that inhibits the growth of tumors and cancers in mammals and can be used to treat viral infections that comprises a fungicide is disclosed. The particular fungicide used is a benzimidazole derivative having the formula: ##STR1## wherein R is selected from the group consisting of H, carboxyl (--CO.sub.2 H), hydroxyl, amino or esters (--CO.sub.2 R') wherein R' is selected from the group consisting of alkoxy, haloalkyl, alkenyl, and cycloalkyl wherein the alkyl groups have from 1-8 carbons or CH.sub.3 CH.sub.2 (OCH.sub.2 CH.sub.2).sub.n --or CH.sub.3 CH.sub.2 CH.sub.2 (OCH.sub.2 CH.sub.2 CH.sub.2).sub.n --or (CH.sub.3).sub.2 CH--(OCH(CH.sub.3)CH.sub.2).sub.n --wherein n is from 1-3, the pharmaceutically acceptable salts thereof, or mixtures thereof.