The objective of this study was to evaluate the effect of cimetidine treatment on cellular immunity in children with Henoch-Schönlein purpura. T cell subset was detected by double marker flow cytometry and the level of IL-2 in peripheral blood was measured by MTT method, before and after cimetidine treatment. The results showed that CD3+, CD4+ T cell subset, CD4+/CD8+ ratio, and blood IL-2 level increased after the treatment (P < 0.05). There was no significant change in CD8+ T subset after the treatment. These findings indicate that cimetidine can promote T lymphocyte proliferation and differentiation, especially TH1 lymphocyte activity.