ABSTRACTAvailable evidence indicates that many of the antiprotozoal drugs currently in use significantly modify the immune response of the host. The effect depends on both the drug and the host. Some drugs enhance the immune response, some are immuno‐suppressants, and others enhance some types of immune mechanisms while suppressing others. Future efforts in the development of antiprotozoal drugs should consider their effects on both the parasite and the immune response of the host. Also in the chemotherapy of protozoal infections consideration should be given to the combined usage of immunoenhancing agents and antiprotozoal drug