Of the cadherin-type Bacillus thuringiensis biopesticide receptors cloned to date, BT-R₁ remains the best characterized regarding toxin binding affinity and specificity. While at least four related clones have been identified in different Lepidopterans, little is known about the tissue distribution or natural function of any of these receptors in insect larvae. The goal of this study was to better evaluate the distribution of processed BT-R₁ mRNAs in Manduca sexta larvae and to search for alternative mRNA processing products which may lead to receptor proteins of differing function or ligand specificities/affinities. Our results in fact indicate that the BT-R₁ mRNA is present only within tissues of the midgut, and that expression is relatively uniform throughout the length of the organ. Due to the lack of related transcripts and alternative splicing products, it is now clear that studies of BT-R₁ isolated from M. sexta midguts indeed involve only a single high-affinity receptor protein.