Seven automobiles were washed and waxed at four car washes. Photographic determinations were made of the glare produced by the wet or dry waxed windshield in a headlight beam. When wet, the waxed windshields scattered three times more light than in the normal human eye. The wet wax scattering was 24.8 times higher than when dry. No wax residues should be permitted on windshields and the National Highway Traffic Safety Administration should issue a mandatory windshield cleaning requirement after waxing.