A method and apparatus for endpoint detection for the stripping of a particular material, such as photo-resist material, from a substrate surface. A beam of light is projected onto the substrate surface and the fluoresced and/or reflected light intensity at a particular wavelength band is measured by a light detector. The light intensity is converted to a numerical value and transmitted electronically to a control mechanism which determines the proper disposition of the substrate. The control mechanism controls the cessation of the stripping process and may control a substrate-handling device which sequentially transfers substrates to and from a stripping chamber.