Inevitably, there were complications: groups of 10 pigs were purchased from University and commercial swine farms and left with their dams for 2-8 days to ensure that they got as much passive immunity from colostrum as possible. Then they were moved to a ''fostering unit,'' developed by the UW Department of Meat and Animal Science, in the FRI animal quarters. This was a box, inside of which were a slanted false floor, thermostatically controlled ventilation system, and dispensing troughs for milk replacer; observation and access were permitted by hinged acrylic panels at the top. The principal purpose of the fostering unit was removing the pigs from potential sources of enterovirus infection long enough to complete testing of the initial fecal specimens before the animals were put into isolators. Even with the colostrum for passive immunity and various other precautions, diarrheal illness occurred frequently, and it was not always possible to keep the pigs healthy and normal (or at times, even alive) to the age of 3 weeks. At approximately 3 weeks, assuming the animals were healthy and had been found not to harbor adventitious enteroviruses, eight of them were moved to individual isolators. Any remaining pigs became donors for kidney cell cultures. The isolators had acrylic fronts and HEPA-filtered air supplies, to preclude non-experimental sources of infection. The animals were fed two meals per day of food produced for human consumption, plus water ad lib. Feeding and watering, as well as emptying the litter trays from beneath the false floors, were done with aseptic precautions. Cages were entered in numerical order, and the pig in cage 8 always served as an unchallenged control. Despite our precautions, on three occasions, 14-day fecal specimens were positive from pigs that had not been challenged, though never from the pig in cage 8. Since the corresponding 7-day specimens had been negative, we surmised that the pigs had become infected while in the isolators, but were never able to determine how this could have happened. In addition to these technical challenges, we learned that well-fed pigs quickly become large and intractable. All suspect results were discarded, and a succinct report of the research was published in the Journal of Food Protection (Cliver 1981) . This was a one-of-a-kind study; we believe that the results (particularly regarding split doses) are significant to the question of peroral infectivity of viruses.