The synthesis and antimalarial activity of a series of 2,4,6-triaminopyrido[3,2-d]pyrimidines (4) is described. Several 6-substituted benzylmethylamino analogues were more active against trophozoite induced Plasmodium berghei in mice than the corresponding quinazoline analogues. These agents, however, are cross-resistant to other antifolate compounds and are thus of limited potential as human agents.