The majority of our virology studies, especially with food, were necessarily performed in the laboratory. All the same, there was a constant urge to look for viruses in the real world of the food chain. The FRI was sponsored by many major food companies, and so it seemed reasonable to approach them first for permission to enter and sample. Few were willing, and many constraints came with the permissions we did receive. Seven plants were eventually sampled, each processing a different group of foods (Kostenbader and Cliver 1977) . In order to deal with this diversity, we developed a sampling plan that was adaptable to all. In order to monitor inputs, we chose to sample: (1) raw materials, (2) water used in processing, and (3) plant personnel. Outputs of the following types were sampled: (1) finished product, (2) by-products, (3) wastes, (4) plant personnel, and (5) wastewater. All the samples were to be tested for ability to produce CPE or plaques in cell cultures. Because of the diversity of samples in prospect, the following types of cell cultures were used as appropriate: primary monkey (Macaca mulatta) kidney, primary swine embryo kidney, chicken embryo fibroblast, HeLa, Vero (Cercopithecus aethiops), and Madin-Darby bovine kidney. Two methods mentioned earlier were quantitatively validated: one entailed inoculation of as much as 1.4 ml of sample per square centimeter of cell monolayer, with subsequent observation for CPE; the second involved testing the same sample in more than one type of cell culture by incubating the inoculum in the first culture for 20 h at 37°C and then transferring the inoculum to another type of cell culture. Both practices were shown to result in minimal loss of viral infectivity, even when the first inoculated culture was an insusceptible cell type, sometimes infected with a competing virus. Processing methods for diverse samples were also validated.