sampling in March 1978. Both immediate follow-up periods extended through September 1979, but a "final" long-term sampling follow-up is planned for November 1980, possibly as a prelude to institution of long-term parasite- suppressive efforts. The treatment plan for the two atolls, though not theoretically ideal, was based on logistical realities as to what would be attainable in the con- text of health surveys and physician visits. Following initial stool surveys, treatment with each agent was to be given at quarterly intervals to all inhabi- tants of the respective atolls except pregnant women and children aged <2 years. Follow-up surveys were to be conducted just before the third quarterly treatment and 9 months thereafter. On Rongelap the schedule was maintained, but ship damage caused schedule alterations during the eradication/suppression attempt on Utirik which resulted in some variation from the treatment/sampling schedules Table 1. attained are shown in Table 1. Sampling (S) and treatment (T) schedules on Rongelap and Utirik Atolls, 1977-1979. w - Ht ' lrHeAaad - 1 i March -m 1978: June September January Utirik wn 1977; Nn Ronge lap June 1979: September January - March - - - June - ~ - September Sampling. S - 1 The actual PraHAi plan. S To the extent that they were in any way reachable, all inhabi- tants of Rongelap Atoll were prevailed upon to submit stool specimens at each sampling period. In spite of strong fecal taboos, samples were obtained from at least 90% of the population by diligent follow-up of dispensed stool containers. The larger population of Utirik (4300) precluded the possibility of total sampling during the limited survey period. Instead, a cohort of 20+% of the population was followed to the extent possible, and was used as an index of the population as a whole. If cohort members were not present on the is- land during a survey (away at school, on a visit, etc.), replacements were picked at random to fill out the three categories: adult males, adult fe- males, and children. Again, diligent follow-up of dispensed containers provided the requisite population samples. Processing of Specimens. An aliquot of 0.5 to 1 g of each specimen returned each day was put into an individually identified l-dram vial - 37 -