The effect of pyrantel pamoate, levamisole, mebendazole, thiabendazole and bephenium hydroxynaphthoate on various intestinal helminths were evaluated among the inhabitants of four villages in the Dezful area southwest of Iran. A total number of 328 persons, all infected simultaneously with Ascaris and hookworm (Ancylostoma duodenale) and 49.2% with Trichostrongylus spp., were randomly divided into six groups. One group was kept as the control and the other five were each treated with one compound. Follow-up examinations showed that all of the drugs used were highly effective on Ascaris, and the differences in the cure rate were not statistically significant except for bephenium hydroxynaphthoate which showed a lower cure rate. For hookworm, cure rates of 100, 90, and 85% were observed with levamisole, pyrantel pamoate and bephenium hydroxynaphthoate, respectively. Cure rates observed with mebendazole and thiabendazole were 35 and 51%, respectively. For Trichostrongylus, the highest cure rate was achieved with levamisole, followed by thiabendazole and mebendazole. While the percentage of people showing side-effects was rather low for all drugs, thiabendazole and bephenium hydroxynaphthoate produced a higher, and levamisole a lower, percentage of side effects.