Plaque development of 42 arbovirus serotypes, representing 17 serogroups, was studied in a clonal line (PS Y-15) of porcine kidney. The arboviruses plaqued within 3 to 7 days, with plaque diameters ranging from 1 to 5 mm. Mouse mortality and cell infectivity end points were compared with 24 arboviruses. Arbovirus LD(50) end points in mice exceeded the porcine kidney monolayer plaque-forming unitage end point with all 24 viruses compared.