The bean leaf beetle (BLB), Cerotoma trifurcata (Forster), is a major pest of snap beans in the eastern and central U.S. Adults can completely defoliate young plants as well as scar bean pods. In order to gain more insight into the impact of BLB defoliation on snap beans we conducted field-cage as well as manual leaf hole-punch studies. Walk-in exclusion cages were used to house snap bean plants in the field containing BLB densities ranging from zero to 115 beetle days per plant. Foliar damage was assessed using a leaf area meter at 30 and 40 days post planting while whole-plant and pod yeilds were assessed at harvest. BLB density had a significant effect on defoliation and leaf area at 30 days after planting, but not at 40 days post planting. Manual defoliation trials simulate early-season feeding as well as season-long feeding by the BLB in snap beans. Defoliation levels were 0, 25, 50, and 75%. There was a significant decline in pod production at greater than or equal to 50% defoliation in both the early-season and season-long defoliation studies. Economic injury levels for early-season snap bean defoliation are discussed.