Population densities of the bean leaf beetle (BLB),Cerotoma trifurcata(Forster), and the portion of the BLB population transmitting bean pod mottle virus (BPMV) were monitored in a soybean field in Lafayette County, Ark., in 1980 and 1981. The spatial and temporal distribution of BPMV-infected soybean plants in two plots within the field also was examined. A peak in the BLB's ability to transmit BPMV occurred between the second and third population density peaks and ca. 12 weeks after planting. The largest increase of BPMV infection level within the plots occurred after the second BLB density peak in the field. Distribution of BPMV-infected plants within the plots was random at infection levels of40%.