During the next year we will continue our immunologic study of human tissue antigens, with special emphasis on alkaline phosphatases (AP) of different tissues and their modifications in tumors. During the last year we have established that approximately 20% of normal human livers contain a minor alkaline phosphatase component which is very similar, but not identical, with intestinal alkaline phosphatase. Since there have been recent reports in the literature that many hepatomas contain a "variant" liver AP which in many respects resembles the minor liver AP component studied in our laboratory, it will be important to obtain hepatomas with this variant and define it in terms of the AP enzymes studied here.