The effect of intravenous immune globulin (IVIG) on the lymphocyte phenotypes in acute Kawasaki disease (KD) was studied in a random trial of IVIG-and-aspirin versus aspirin-alone. Before therapy, patients in each treatment group had an increased percentage of B cells, and a decreased percentage of T cells, CD4 T cells, CD8 T cells and CD5+ B cells. There was no significant difference in immunologic parameters between the two groups measured before therapy. Patients treated with IVIG-and-aspirin had by the fourth day developed a highly-significant increase in T cells, CD4 T cells and CD8 T cells and a decrease in B cells. Despite the decrease of B cells, there were significant increases in CD5+ B cells in both treatment groups. However, the degree of increase in the IVIG-and-aspirin treated group was significantly more noticeable than that in the aspirin-alone treated group. These findings indicate that treatment with IVIG restores the T- and B- cell abnormalities, especially CD5+ B-cell abnormalities found in patients with acute KD.