Abstract: A method and apparatus for the stimulation of biological processes related to cellular activity, particularly for promoting the healing of lesions on the body-surface, i.e. wounds, ulcers and epithelial injuries.The lesion is irradiated with linearly polarized light of predetermined intensity, comprising incoherent components of wavelength, exceeding 300 nm.The apparatus comprises a light source, constituted by a lamp emitting incoherent visible and/or infrared light, a deflecting system projecting the light beams into the given direction of treatment, a polarizer placed in the path of the light beam, projected into the direction of treatment, and preferably ultraviolet and infrared filters.