Stereological analysis of normal Papio Papio liver parenchymal cells has been performed according to the method of Weibel (1969). The study was carried out on liver samples collected from 3 males and 3 females. Sampling was done at three levels of magnification (X 250, X 5 000, X 15 000) without taking into consideration the lobular variations. The lobular stereological model included the hepatocyte, all the cellular organelles and the extra-hepatocytic space compartment. Surface and volume densities were determined; the results are given with respect to three reference units : 1 cm3 lobular tissue, 1 cm3 hepatocyte and 1 cm3 hepatocytic cytoplasm. The mean volume of the Baboon hepatocyte and its components were also measured. Statistical analysis of the results did not show wide individual variation in the population studied. The volume densities of the components were compared to those of rat, dog and man as determined by other investigators. The hepatocytes constitute 84,9% of the lobular volume, and the extra-hepatocytic space 15,1%. The mean individual volume of the hepatocyte is 6 470 micrometer3, which is higher than in rat and dog. The smooth endoplasmic reticulum has a much higher surface density (3,93 m2/cm3) than that of the rough endoplasmic reticulum (1,53 m2/cm3). The values obtained in the present study can be used as reference values in the evaluation of experimentally induced hepatic modifications in Baboon.