Liver samples were taken from previously anaesthetised Sprague Dawley rats, both normal and irradiated with daily doses of 1, 2, 4, 8, and 16 J/cm(2) applied over 15 days by AsGa laser equivalent to 904 nm. These samples were then processed for optical microscopy. They were studied and subjected to morphometric techniques using 1000X magnification, placing special emphasis on the quantification of the areas of nuclei and nucleoli. An analytic comparison of the results between normal and irradiated hepatocytes reveals the existence of significant differences between both the nuclear and nucleolar areas studied, from which it is concluded that the effect of these doses of infrared radiation is to provoke a drastic transformation in the components of the hepatocytes, and therefore in their functioning, principally with respect to protein synthesis, and that this would be the effect of stimulation of this nature on this type of high-metabolism cell.