Levamisole is a drug of choice for treatment of ascariasis. With recommended dosages, it is virtually free of side effects. Single doses of 50 to 150mg will eliminate all parasites in 90 to 100% of ascariasis patients irrespective of worm burden. Activity against hookworms has been demonstrated for levamisole but the most effective treatment regimen has not been determined. Further drug trials are needed for better assessment of efficacy. Levamisole has little or no curative action on infections with whipworms and pinworms. It may have some activity against strongyloides but confirmatory studies are needed. It has been shown that levamisole has significant activity against microfilariae of Wuchereria bancrofti and Brugia malayi. It is not, however, as effective as diethylcarbamazine ('Hetrazan'), and side reactions are greater. In tolerated doses, levamisole does not have significant action on adult forms or microfilariae of Onchoceea volvulus. The drug applied topically, however, may find a place in treatment of ocular onchocerciasis. Limited trials with levamisole for toxoplasmosis and chronic cutaneous leishmaniasis have given promising results, and further studies are indicated.