It is estimated that over 1,100,000,000 persons the world over are infected with helminths.51 In underdeveloped countries, the burden of helminth infection, added to that of malnutrition and bacterial, protozoal, and viral infections, may be the proverbial back‐breaking straw. Well‐nourished persons often harbor helminths without apparent damage and one may question the wisdom of treating such infections, especially with chemotherapeutic agents with toxic qualities. On the other hand, if a safe and effective drug is available, treatment should be given until evidence is in hand that these helminth infections do not harm or are beneficial to man. Unfortunately, reinfection is common and prompt unless sanitary measures are instituted. Although pinworm frequently causes man little or no inconvenience, and light infections of other worms may go unnoticed, hookworm and schistosomiasis are debilitating and deadly infections. Heavy infection with many other helminths may cause very serious anemia, and the normal and aberrant wanderings of several species may be fatal.