Eleven patients with early CLL (two in Rai's stage 0, seven in stage I, and two in stage II) received aIFN (3 MU subcutaneously three times a week for a median of 8 months; range, 4-12) after their tumor mass had been reduced with intermittent chlorambucil. Following chlorambucil/aIFN administration, a significant reduction in blood lymphocyte counts (from 25.1 +/- 12.0 x 10(9)/l to 6.3 +/- 5.32 x 10(9)/l; p less than 0.001) and in CD 19-positive cells (from 21.0 +/- 12.0 x 10(9)/l to 3.8 +/- 2.3 x 10(9)/l; p less than 0.001) was observed. Three of seven patients with stage-I and one of two with stage-II disease moved to stage 0, and a complete response (CR) was observed in two patients with stage-I at diagnosis. Overall, there were eight patients who, after treatment, had either a CR (2 cases) or stage-0 disease (6 cases), which compares favorably with two patients with stage-0 disease before entering the study (p = 0.015). In five patients (including the two who achieved a CR) aIFN further improved the disease status achieved with chlorambucil.