A total of 44 patients were treated with intensive induction chemotherapy for acute nonlymphocytic leukemia (ANLL). A complete remission (CR) was obtained in 29/44 (66%) patients. Serum zinc (Zn) and copper (Cu) were studied as possible prognostic factors in the determination of the chance of a patient attaining remission. Pretreatment Zn was higher in patients attaining a remission (0.99 +/- 0.05 microgram/ml) than in patients failing to attain a CR (0.78 +/- 0.06 microgram/ml) (P = 0.0216). There was no further difference between the two groups during aplasia. However, when response to treatment was evaluated about day 28, the difference reappeared: 1.06 +/- 0.05 microgram/ml for CR patients vs 0.77 +/- 0.07 microgram/ml for failures (p = 0.0012). Pretreatment Cu was higher in responding (1.44 +/- 0.07 microgram/ml) than in nonresponding (1.06 +/- 0.05 microgram/ml) patients (p = 0.0002). The difference between the two groups remained highly significant at days 7, 14, 21, and 28. At the time of response evaluation, the values were 1.46 +/- 0.05 microgram/ml for CR patients vs 1.19 +/- 0.08 microgram/ml for non-CR patients (P = 0.0070). We conclude that the measurement of serum Zn and Cu may be helpful in the prediction of response to chemotherapy in patients treated for ANLL.