When 37 patients whose stools were positive for Enterobius were treated with 1.0 gm. of piperazine citrate twice daily for six days, and then 1.0 gm. twice a day for two consecutive days each week for 14 months, 91 per cent were negative after 3 months and all after 5 months; all remained negative after 14 months. When six patients were given 2.0 gm. of piperazine citrate once a week for a year 3 were negative after 2 months of treatment and all after 3 months, and all of these remained negative for the rest of the year.