A unique effect of the polyethoxylated (average 5 ethylene oxide units, EO 5) octylphenol surfactant, Triton X-45 (TX-45), on the sorption and penetration of 2- (1-naphthyl) [1-¹⁴C] acetic acid (NAA) by and through enzymatically isolated tomato fruit cuticular membranes (CM) is described. TX-45 induced an unusually marked increase in cuticular sorption (55% greater than control) of NAA relative to Triton X surfactants of lower and higher EO content. This marked enhancement of NAA sorption was associated with epicuticular and cuticular waxes, for on removal of waxes, the TX-45 — mediated increase in sorption was lost. Surprisingly, a different lot of TX-45 failed to produce similar results. Evaluation of eight lots of TX-45 (0.1 % w/v) revealed that three produced no enhancement while five increased NAA sorption. A TX-45 lot that enhanced NAA sorption also increased NAA transcuticular penetration of isolated tomato fruit CM in a finite-dose diffusion system. Again, the CM waxes played a critical role. Based on capillary gas-liquid chromatography, no obvious differences were found in the ethoxymer profile of selected nonenhancing and enhancing TX-45 surfactants that could be related to performance.