This paper deals with MN blood grouping of stains of organ homogenate and thin organ sections by means of an elution test in combination with antiglobulin test. Each stain of the liver, spleen, brain, heart, lung, thyroid, kidney and muscle homogenates gave evidently M and N blood group activities in accordance with those of sources. It was considered that non specific adsorbing potency of the human organ was eliminated in the procedure of homogenate-staining. However, examination on sections showed frequently unsatisfactory results. It was attributed to non-specific adsorption of sections with anti-M and -N antibodies. The present findings may offer a valuable information to identify human tissues in forensic practice.MN blood group; organ antigen Many efforts to detect MN blood group of human organs have been made, but few satisfactory results have been obtained yet. In the preceding paper (Sagisaka and Tokiwa 1973), MN blood group activity of the blood components other than red cells was detected by an elution method in combination with antiglobulin test. The organ homogenate stained on gauze and thin organ sections were examined by the same method.The human organs; liver, spleen, brain, heart, lung, thyroid, kindey and muscle, were excised from corpses one to three days after death.The organs were homogenized in an equal weight of saline by a Potter-Elvehjem homogenizer.The homogenate was dropped on a clean gauze and dried at room temperature.MN blood grouping was performed on two threads of the gauze or a piece of the sections by an elution method in combination with antiglobulin test as described in the previous paper (Sagisaka et al. 1971). After fixing at 100•Ž for 10 minutes, two threads of the gauze, 1 cm in length, were teased apart and washed once with saline to remove insoluble materials. The sensitized fibrils were washed with cold saline two times, which was able to eliminate the non-specific antibody reacting with stains. As controls, stains of the ten-fold diluted red cells, which were prepared 2 years ago, were tested. Each stain of the homogenates had evidently M or N blood group activity in accordance with that of the sources (Table 1). The M and N activities were, as a rule, not so low as compared with those of the controls.Comparing M and N activities of each organ, the spleen and Received for publication,