This paper is intended to report the results of whole-body autoradiography and microautoradiography of mice having Ehrlich's tumor, and also to report the summerized clinical data so far studied. The accumulation of67Ga-citrate in the tumor cells was elucidated both by chemical analysis in preliminary report and by autoradiogram in this report. The mechanism of accumulation is still unknown but there seems to be some correlation to the cell function. Clinical studies on about 50 cases of malignant tumors with67Ga-citrate have proved to be satisfactory. Especially, 67Ga-citrate is valuable to establish the diagnosis of cancer of lung, breast and maxilla, however, it is rather difficult, at present, to obtain positive scintigram in the case of cancer of stomach, pancreas, liver and esophagus. There is a possibility that67Ga-citrate may be uptaken into the benign tumor or inflammatory lesion. According to our experience, however, all of the benign lesion consisting of 2 cases of frbroadenoma and 5 cases of cystic disease of the breast, except one case, showed negative scintigram. We believe that clinical usage of67Ga-citrate is valuable to make a differential diagnosis of benign and malignant diseases. Uptake into the inflammatory lesion seems not to be significant comparing with that into the malignancy. However, further investigations might be necessary, because uptake into the inflammatory lesion seems to be different depending upon the site and type of the lesion.