A single dose of syrup containing piperazine citrate was almost always completely effective in eliminating light, moderate and heavy infections with Ascaris lumbricoides with the dosage employed. There was no evidence of intolerance to the drug. The worms were still living and intact when eliminated. The preparation of the drug used is a pleasant tasting syrup, facilitating the treatment of small children. This effective single dose therapy, without local or systemic hazards and requiring no fasting or purgation, should be suitable for mass treatment of patients with ascariasis.