Despite many years of research on the mode of action of the pore-forming three-domain Cry toxins from Bt, not until 2010 was there any inkling that ABC transporters could play a role. Positional cloning identified members of the ABCC family in Cry1Ab or Cry1Ac-resistant strains of three different moth species. Unlike previously-identified Cry toxin receptors, the ABCC proteins lack a large extracellular domain that could be characterized and isolated on the basis of toxin binding affinity, and no biochemical method had been able to reveal them as Bt targets. Subsequent work in insects has identified ABCC transporters as targets of the Cry1A toxins, ABCA transporters as targets of the Cry2 toxins, and ABCB transporters (P-glycoproteins) as targets of the Cry3 toxins. CRISPR/Cas9 knockouts of these transporters are usually not lethal, but they confer extremely high levels of resistance to the cognate toxins, higher than knocking out any other binding target. We have hypothesized that the ATP-switch mechanism of ABC transporters provides the conformational change required to drive the Bt pore into the lipid bilayer. We will discuss the types of evidence that will be required for a strong test of this hypothesis. Despite the availability of crystal structures of the toxin monomer in solution and the protoxin in the parasporal crystal, structural evidence lags far behind that of many other bacterial pore-forming toxins. This deficiency must be remedied if significant progress is to be made in devising counterstrategies to Bt resistance, which is now evolving in some key insect pests of agriculture.