An enhancer element was identified in the virus Orgyia pseudotsugata multicapsid nuclear polyhedrosis virus (OpMNPV) that is located adjacent to the 3' end of the IE-2 gene and 5' to an open reading frame that codes for a predicted protein that has 37% homology to the AcMNPV PE-38 gene. The OpMNPV enhancer (OpE) consists of a 66-bp element that is tandemly repeated partially or completely 12 times. The OpE sequences were shown to increase gene expression from the Autographa californica MNPV delayed early p39 promoter independently of position or orientation, and were also shown to increase expression from the promoter of the OpMNPV immediate early gene, IE-2. Sequences homologous to the OpE sequences were mapped by Southern blot hybridization to four additional locations around the OpMNPV genome. This indicates that OpMNPV is similar to other baculoviruses such as AcMNPV, Lymantria dispar MNPV, and Choristoneura fumiferana MNPV that have homologous regions in several locations in the genome.