A series of 6-[(arylamino)methyl]-2,4-quinazolinediamines have been prepared by catalytic hydrogenation of the requisite 2,4-diamino-6-quinazolinecarbonitriles in the presence of the appropriate benzenamine. Formylation, acetylation, and nitrosation provided N omega derivatives of these compounds. A variety of the compounds exhibited potent antimalarial, antibacterial, and antitumor activity. In particular, 5-methyl-6-[[(3,4,5-trimethoxyphenyl)-amino]methyl]-2, 4-quinazolinediamine (trimetrexate, 15) has shown a broad spectrum of antitumor effects and is undergoing preclinical toxicology evaluation prior to trial in man.