Twenty-four four-month-old female rats weighing approximately 250 grams were divided into four groups labeled A, B, C and D. A corresponds to the normal group and the other groups received stimulation increasing doses with 4, 8 and 16 J/cm(2) of infrared laser respectively for 15 consecutive days in five points of the liver. The rats were then sacrificed and samples of normal liver and liver stimulated with infrared inductions were extracted for immediate processing via transmission electron microscopy. From cell types transmission electron microphotographs were obtained at magnifications of 9500 X these were subjected to morphometric studies to determine volumetric fractions of the nuclei and nuclear structures. Likewise, cell and nuclear areas and nuclear-citoplasmatic relation were quantified. Analysis of the results between normal and radiated hepatocytes revealed notable differences in all the cell components quantified. It is concluded that the effects of increasing infrared stimulation doses brings transformation in their ultrastructure and morphology, fundamentally in the considerable increase in nuclear volume, chromatin volume and the nuclear-citoplasmatic relation, which ultimately translates into a functional variation, thus representing an obvious impact produced by these infrared inductions.