Univalent oxidation of luminol and univalent reduction of lucigenin must precede reaction with O2.- if that reaction is to lead to luminescence. The assumption that luminol or lucigenin, per se, reacts with O2.- in a way leading to luminescence is incorrect, and leads to misinterpretation of results. The chemical reactions leading to the O2(.-)-dependent luminescences of luminol and of lucigenin are discussed.