Predictions based on the Gypsy Moth Event Monitor and the Stand Damage Model were compared to remeasurement plot data from long-term studies which received gypsy moth defoliation. Data were from three studies located in the Appalachian hardwood region and the Atlantic Coastal Plain. Projection errors, in terms of trees per acre and basal area per acre, were examined. The Stand Damage Model underestimated trees per acre and basal area per acre for all simulated stands. The Gypsy Moth Event Monitor modified Forest Vegetation Simulator underestimated defoliation events, especially those of high intensity; however, these errors were often reduced over time by scheduled outbreaks. Gypsy Moth Event Monitor projections performed most accurately on stands where actual mortality increased slowly over the course of the simulation. The Gypsy Moth Event Monitor underpredicted basal area per acre for all stands which experienced increasing actual basal area during the projection period.