Abstract: Objective To study the changes of Tlym phocyte and natural killer(NK)cells in small children with measles.Methods Peripheral blood cells were stained with antibodies labled fluore scecse.T-lymphocytes and NK cells were counted with flow cytometry in measles patients(n=174,age=6 months 6 years)and normal controls.Results Compared with the control group,the percentage of T-lymphocyte and NK cells in children with measles-infecton was signifi-cantly increased(P<0.05).The percen tages of CD₃,CD₄ and CD₄/CD8 were not significantly different between measles patients and control group(P>0.05).The counts of CD₃ and CD₄ cell in groups with high viral activity were significantly lower than those of the low-activity groups(P<0.05).While there was no difference in the counts of CD8 and NK cell between high-activity group and low-activity group(P>0.05).Conclusion To understand the changes of Tlym phocyte and NK cells in children with measles is he lpful to evaluate the patients' cellular mimune status and to predict the replica tion of measles virus.