ABSTRACT A study was initiated in 2003 and continued in 2004 to examine the species diversity of forest Lepidoptera and determine larval parasitoid assemblages in forest fragments in northwest Ohio. Three primary questions are being addressed: 1) Is the diversity of Lepidoptera lower in small compared to large forest fragments? 2) Is the percentage of Lepidoptera larvae attacked by insect parasitoids lower in small forest fragments compared to large forest fragments? 3) Is the larval parasitoid diversity lower in small fragments versus large fragments? We selected 12 forest fragments ranging from 5 ha to over 1000 ha. Beginning in the third week of June, 2003, and the third week of May, 2004, we sampled each woods every 3-4 weeks over the summer and early fall, collecting as many larvae of tree-feeding Lepidoptera as possible during each visit. Species from the lepidopteran families Arctiidae, Geometridae, Notodontidae, Noctuidae, Coleophoridae, Gelechiidae, Nymphalidae, Lymantriidae, Sphingidae, and Saturniidae were collected. Caterpillars were reared in the laboratory on their host plant material until they completed development or until parasitoids emerged. There appeared to be no apparent effect of wood fragment size on either species richness or levels of larval parasitism of forest Lepidoptera. Nearly all larval parasitoids reared from collected larvae were from the families Braconidae and Ichneumonidae. Parasitoid species diversity remains to be determined.