4, 4 ″-Diamidino-m-terphenyl (1) and 36 analogues were prepared and assayed in vitro against T rypanosoma brucei rhodesiense, Trypanosoma cruzi, Plasmodium falciparum, and Leishmania amazonensis. Twenty-three compounds were highly active against T. b. rhodesiense or P. falciparum. Most noteworthy were amidines 1, 10, and 11 with IC50 of 4 nM against T. b. rhodesiense, and dimethyltetrahydropyrimidinyl analogues 4 and 9 with ...