In 1995 and 1996, Lepidoptera larvae of 13 families were sampled by pruning foliage from canopies of maple, hickory, red oak group, white oak, and chestnut oak. The families were Arctiidae, Geometridae, Hesperiidae, Lasiocampidae, Lycaenidae, Lymantriidae, Noctuidae, Notodontidae, Nymphalidae, Papilionidae, Saturniidae, Sphingidae, and Thyatiridae. Samples were collected from 18 plots (each 200 ha), nine in the George Washington National Forest in Virginia and nine in the Monongahela National Forest in West Virginia. Sampling seasons were from May to mid-August; foliage samples were collected each week. The occurrence of Lepidoptera on host trees within the two forests was compared. A total of 131 species of caterpillars representing 13 families was collected. Most larvae were Noctuidae (47 species) and Geometridae (44 species). Of 6,743 larvae collected over both years, 57% were gypsy moth, Lymantria dispar (L.). The population of this species collapsed during the second year of the study because of the fungus Entomophaga maimaiga. Other particularly abundant species in both forests were Acronicta ovata Grote, Hyphantria cunea (Drury), Polia latex (Guénée), Melanolophia canadaria (Guénée), Alsophila pometaria (Harris), and Nadata gibbosa (J.E. Smith). Some species were found only in one forest. Larval richness and abundance were higher in May and August and the lowest numbers occurred in June and July. Abundance and richness were different for the 2 yr. Population shifts may be directly related to weather conditions or indirectly related through the effects of temperature or rainfall patterns on natural enemies, foliage chemistry, or other factors. The number of species of caterpillars collected from the host tree groups was 62 on maple, 77 on hickory; 76 on the red oak group, 75 on chestnut oak, and 66 on white oak. The abundance of larvae ranged from 14.8% collected on maple to 25.4% collected on the red oak group.