A leukemia-associated antigen, CAMAL, shown to be present in bone marrow (BM) cells from patients with acute nonlymphoblastic leukemia (ANLL) even during remission, has been examined using indirect immunoperoxidase and a monoclonal antibody, CAMAL-1. We are ending the third year of an ongoing blind study designed to monitor the number of BM cells expressing the CAMAL protein (CAMAL BM value) in ANLL patients over the course of their disease. Results thus far have revealed that the CAMAL BM value in individual patients often changed significantly post-chemotherapy. This change appeared to be a useful prognostic marker in many instances. ANLL patients at initial presentation whose CAMAL BM values increased or stayed the same post-chemotherapy had significantly (p less than 0.025) shorter remission lengths (x = 6.8 months, n = 24) than those whose CAMAL BM values decreased (x = 19.2 months, n = 10). There are indications that increasing CAMAL BM values during remission occur prior to clinical relapse.