The authors describe research results on five patients suffering from acute leukemia. In each case the first diagnosis is given, followed by the treatment, and a second diagnosis is quoted after an interval of a few years. One patient had cancer of neck and breast and two had Hodgkins disease according to the first diagnosis. In each case the second diagnosis was acute or smouldering leukemia. The treatments applied include radiotherapy, some surgery and applications of drugs. Details are given for each case in turn.