Objective:To detect lymphocyte subsets in the peripheral blood of patients with different types of severe drug eruption and study its clinical significance. Methods:Immunofluorescence flow cytometry was performed to analyze the phenotypes of peripheral blood cells in 21 patients with severe drug eruption. Results:CD3+,CD3+CD4+ lymphocytes of the peripheral blood in drug-induced hypersensitivity syndrome (DIHS) patients was significantly increased in comparison with the normal value,and CD3+CD4+ lymphocytes of the peripheral blood cells in DIHS patients was significantly higher than that in Stevens-Johnson Syndrome (SJS) patients and toxic epidermal necrolysis (TEN) patients. With the increase in the number of CD3+CD4+ and CD3+CD8+ lymphocytes in the peripheral blood cells,the maximum dosage of corticosteroids progressively decreased in SJS and TEN patients. With the increase in the number of CD3-CD16+CD56+ lymphocytes of the peripheral blood cells,the maximum dosage of corticosteroids progressively increased in SJS and TEN patients. Conclusion:Different types of severe drug eruption have different lymphocyte subsets in the peripheral blood,which have different effects on the maximum dosage of corticosteroids.