Field trials were carried out to evaluate whether folpet sprayed on grapevines penetrated the epicuticular wax and cell walls of grapes. Folpet showed poor penetration into the epicuticular wax; it was found almost totally on the surface. Despite its low solubility in water, perhaps due to the presence of adjuvants, its residues showed such a high resistance to washing that the action of rain was negligible in decreasing residues.