The cDNA sequence of the α6 nicotinic acetylcholine receptor subunit of diamondback moth (Plutella xylostella) was cloned and sequenced. Transcripts were similar between the spinosad-susceptible G88 and Wapio strains. All transcripts from the spinosad-resistant Pearl-Sel strain contained premature stop codons, and most transcripts have not been previously reported. None of these truncated transcripts were seen in the spinosad-susceptible strains. Proteins made from these transcripts would likely have no, or greatly altered, receptor function. An F(2) backcross and spinosad bioassay showed that all spinosad bioassay survivors produced truncated α6 transcripts. Thus, it appears that spinosad resistance in diamondback moth is due to a mutation(s) that results in no functional Pxylα6 being produced.