The reversible mitochondrial transhydrogenase in Manduca sexta has been characterized and is involved with endocrine-mediated post-embryonic larval development in this model insect. While biochemical in vivo and in vitro studies have been accomplished, robust molecular studies of the transhydrogenase have not been possible due to deficient genomic data. In the present study, using a combination of degenerate oligonucleotide primers and raw genomic data, we have determined the structure and sequence of the transhydrogenase gene from the model insect Manduca sexta. The encoded protein is highly similar to other transhydrogenase proteins and this sequence is the first lepidopteran sequence reported to date.