Chemotherapy against protozoan diseases has been practised since ancient times. Although still widely used, antiparasitic drugs are seldom completely effective. Complete elimination of an extensive protozoan infection usually requires a combination of drugs which target parasitic mechanisms very similar to the human host, as manifested by a multitude of side effects of varying severity. Furthermore, there is an escalating problem of widespread resistance to commonly used chemotherapeutic agents. Here we present an alternative strategy for the design of antiprotozoal agents using the principal enzyme involved in DNA replication as a possible drug target--DNA polymerase.