In the present study, we investigated whether oral ingestion of Echinacea purpurea improves human immunity, especially of NK. cells, T-lymphocyte, and B-lymphocyte. Twenty two healthy volunteers, who feel fatigue daily, participated in our trial, and were randomly assigned to either the echinacea group or placebo group. The echinacea group ingested a preparation of Echinacea purpurea which consisted of 500mg of extracts of Echinacea purpurea and 1500 mg of diluents, whereas the placebo group ingested a placebo which consisted of 2000mg of diluents. Each participant ingested test products once a day before sleeping, for 3 weeks. We inspected the participants' immunity at initial, 1 week, and 3 weeks after the ingestion. Scoring of Immunological Vigor, which is the comprehensive assessment of human immunity, significantly improved only in the echinacea group (p= 0.030). As compared with the initial level, the growth of the numbers of lymphocytes (p=0.035) and CD4+ T-ce!ls (p=0.050) in the echinacea group at 3 weeks after the initiation of ingestion significantly increased more than those in the placebo group, and the growth of the number of T-cells (p=0.060) showed the same tendency with marginal significance. However, the number of NK-cells and its activity in both groups decreased, and the number of B-cells did not show any significant change. In summary, our results indicate that preparation of Echinacea purpurea could improve the immunological function of humans, especially in T-lymphocyte.