A headspace, gas chromatography-mass spectrometric (GC-MS) method for the identification and quantitation of 1,4-dioxane in polyethoxylated surfactants is described. An isotope dilution method employing 1,4-d8-dioxane has been used for the quantitation of 1,4-dioxane which is based on the determination of the molecular ion (mass 88) by MS. The detection limit of the method was 0.3 ppm 1,4-dioxane. 82% of the cosmetic products investigated were found to contain 0.3–96 ppm 1,4-dioxane, and 85% of the products for dish washing investigated contained 1.8–65 ppm 1,4-dioxane.