We were offered a small grant by the International Atomic Energy Agency to look further into this process. With this and limited support from other sources, we planned to produce the viruses in Madison and send them to Lowell to be inoculated into the shellfish and irradiated as was done in the earlier study, with the soft tissue shipped back frozen for assay in our laboratory. Extraction of the virus was to be done by our ''Cat-Floc'' method (Kostenbader and Cliver 1981) . Because of the high cost of irradiation, we mixed poliovirus 1 (PO1) with HAV, so that they could be inoculated and irradiated together. When the virus mixtures were inoculated onto FRhK-4 cell monolayers, PO1 plaques were seen within 5 days; however, if the mixture was treated with anti-PO1 antiserum before inoculation, then HAV plaques were seen at approximately 16 days of incubation, and the PO1 was not expressed. This also worked with the shellfish extracts-to our knowledge, this approach has not been used by others, although mutually exclusive host systems have permitted inactivation studies on mixtures of two animal viruses and two phages (Olivieri et al. 1983 ). The first shipment of viruses was lost in transit to Lowell, so another had to be sent. Eventually, the samples arrived back in Madison for extraction and assay. Calculated D 10 values for viruses in clams (PO1, 5.43 kGy; HAV, 5.95 kGy) were higher than those reported by others (Fig. 1) , perhaps due to matrix effects and the different extraction procedure. Unfortunately, the laboratorian (Kenneth D. Kostenbader, Jr.) developed a fatal illness, and the oyster samples were not assayed, nor have the results presented here been published elsewhere.