As a powerful tool of cell screening and cell purification, we developed a novel method to kill adherent cells as cultured on a substrate by micro-projection of incoherent visible light. To kill the cells by the mild light irradiated by electrically controllable micro-projection systems currently available, we introduced the assist of the photo-responsive culture substrates functionalized with a photo-acid-generating polymer. In clear contrast to the existing laser-based methods requiring point scanning, areal micro-prjection of blue light with the wavelength 436?nm killed many CHO-K1 cells at a time in the irradiated area on the substrate. The effect of the photo-generated acid was so confined that selective killing of targeted cells was achieved without critical damage to the neighboring cells. Further, we demonstrated the photo-selective killing of the adherent cells after preliminarily patterning through the photo-induced removal of cell adhesion-inhibiting polymer. Biotechnol. Bioeng. 2013; 110: 348352. (C) 2012 Wiley Periodicals, Inc.