The lymphatic stomata in the pelvic peritoneum of human fetuses and mature mice were initially observed and studied quantitatively by using computer image processing (C.I.P.) attached to a scanning electron microscope (SEM). Two types of mesothelial cells were found in the pelvic peritoneum of human fetuses and mature mice, i.e. flattened and cuboidal cells. The lymphatic stomata, arranged in clusters, were only found irregularly distributed among the cuboidal cells. The divergence of stoma area in the pelvic peritoneum of human fetuses varied greatly, ranging from 0.8 micron2 to 43.4 microns2. The average area of the lymphatic stomata in human fetuses was 10.00 +/- 9.44 microns2. The variation coefficient was 94.40. The standard deviations and standard errors were 9.44 and 0.98 respectively. Most of the lymphatic stomata in human fetuses were between 1.34 microns2 and 32.11 microns2 in size (accounting for 90%), with maximum and minimum values of 43.4 microns2 and 0.8 micron2. The average distribution density of the lymphatic stomata in human fetuses was 7.2% and the maximum density was 11.6%, which means that the average and the maximum absorption rates of the human pelvic peritoneum from the peritoneal cavity were 7.2% and 11.6% respectively. Therefore, it is suggested that the lymphatic stomata in pelvic peritoneum play an important role in draining materials from the peritoneal cavity, and that the absorption effect of the pelvic peritoneum is similar to that of the diaphragmatic peritoneum.