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 (—CO₂H), hydroxyl, amino or esters (—CO₂R) wherein R is selected from the group consisting of alkoxy, haloalkyl, alkenyl, and cycloalkyl wherein the alkyl groups have from 1-8 carbons or CH₃CH₂(OCH₂CH₂)_n— or CH₃CH₂CH₂(OCH₂CH₂CH₂)_n— or (CH₃)₂CH—(OCH(CH₃)CH₂)_n— wherein n is from 1-3, the pharmaceutically acceptable salts thereof, or mixtures thereof.