Attempts at suppression of endemic intestinal helminths on Rongelap and Utirik, with a different regimen on each, underlined the effectiveness of mebendazole (the more costly) and raised serious questions as to the effectiveness of the recommended dosage of pyrantel pamoate under the logistic constraints of the timing of BNL visits to the outer atolls. Of considerable significance in the context of suppressive treatment is the prolonged suppression of parasitosis obtained with mebendazole, as well as its attainable effective- ness against all three endemic helminth parasites. Even 9 months after the last of three quarterly treatments, Ascaris and Trichuris prevalence was reduced by 84.7% and 72.3%, respectively. This suggests that, notwithstanding the arrival of parasitized persons on the quarterly Marshall Islands "field trip" ship - as was also occurring during the survey period - treatment of the entire population every six months (after an initial three-quarterly suppres- sion) should keep these atolls at a very low level of helminthic infection (this would be especially true if preventive treatment were given to all persons coming from infected areas at the time of their disembarking from the Marshall Islands vessels). Such a program could be instituted as early as November 1980, beginning with a complete parasitic survey, provided that mebendazole were available and that a conscientious health aide could be re- cruited to ensure both complete population treatment and treatment of all per- sons disembarking from Marshall Islands ships. With such conscientious suppression, virtually complete freedom from intestinal helminths could be anticipated in a very few years. Suitable measures against pathogenic intestinal protozoa could also be anticipated in due course. - 42 +