A series of bis-2,5-[4-guanidinophenyl]thiophenes were prepared in a five step process starting from 2,5-bis[trimethylstannyl]thiophene. The compounds were evaluated in vitro against Trypanosoma brucei rhodesiense (T. b. r.), Plasmodium falciparum (P. f.), Leshmania donovani (L. d.) and Trypanasoma cruzi (T. c.), and in vivo against T. b. r. Certain compounds show promising in vitro activity against T. b. r. and P. f. and have superior in vivo activity against T. b. r. to that of pentamidine and furamidine.