Gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), multicapsid nucleopolyhedrovirus (LdMNPV) has been registered as a microbial pest-control product in the United States (Gypchek®) and Canada (Disparvirus®). Similarly, Douglas-fir tussock moth, Orgyia pseudotsugata (McDunnough) (Lepidoptera: Lymantriidae), multicapsid nucleopolyhedrovirus (OpMNPV) is registered in the United States and Canada as TM BioControl-1® and a product derived from TM BioControl-1 (Virtuss®) is also registered in Canada. To determine changes that may have occurred in these products over time, we compared DNA from Gypchek with Disparvirus and DNA from TM BioControl-1 with Virtuss using restriction fragment length polymorphism (RFLP) analysis. Gypchek and Disparvirus showed the same RFLP banding patterns when viral genomic DNA was digested with BamH I, EcoR V, and Hind III and only a single band difference at approximately 1.6 kilobase (kb) when digested with Bgl II. TM BioControl-1 and Virtuss showed no differences in genomic DNA when digested with Bgl II, Sam I or Hind III. Twelve viral open reading frames (ORFs) were amplified from Gypchek and Disparvirus and nine from TM BioControl-1 and Virtuss by polymerase chain reactions (PCR). The amplified ORFs ranged from highly conserved (polyhedrin) to least conserved (vp91 capsid associated protein). The products were sequenced and the deduced protein products compared. Amino acid sequences deduced from the sequenced PCR products indicated that 8 of the 12 proteins were identical in the two LdMNPV products. The four proteins showing minor sequence variations were DNA polymerase, LEF-8, P74 envelope protein, and VP 91 capsid associated protein. No differences were detected in the protein products deduced from the nine sequenced ORFs from TM BioControl-1 and Virtuss. Comparative RFLP and protein phylogenetic analyses of Gypchek with Disparvirus and TM BioControl-1 with Virtuss revealed little difference between the respective LdMNPV and OpMNPV populations that make up these product pairs.