The emergence of new parasitic diseases has encouraged studies on the elucidation of the mode of action of new and old antiparasitic drugs, and has led to the development of new chemical series. Resistance occurs rapidly when a single drug is used massively in human and animals. A better knowledge of the mode of action allow synergistic combination of compounds, slow-release devices proposed for cattle. Another alternative is to improve bioavailability of antiparasitic drugs by targetting at the parasite molecular level with prodrugs, drug-carriers as liposomes, nanoparticles. The use of new compounds should be expected with relative optimism.