Levamisole (Decaris, Belgium) was tested in Iran, Brazil, and in Mississippi and Louisiana for its efficacy as a single-dose oral treatment forAscarisinfections. Subjects were children ages 2 to 15 years, and numbers treated with levamisole and comparative anthelminitics are as follows: 453 with levamisole; 461 with piperazine citrate; 17 with pyrantel pamoate; and 19 with a placebo. Cure rates and total reduction in mean egg counts observed were 92% and 98% respectively for levamisole and 66% and 90% for piperazine. Sixteen of 17 treated with pyrantel pamoate were cured. In none of the drugs were there notable side reactions, but in all four studies side effects were more frequent with piperazine than with levamisole. Levamisole was found to be a well-tolerated, highly effective single-dose ascaricide. It should prove to be particularly useful for mass chemotherapy inAscariscontrol programs.