OBJECTIVE: This study examined the serum levels of T cell subgroups and immunoglobulins in children with Mycoplasma pneumoniae pneumonia (MPP) in order to investigate the patients' immune function. METHODS: Flow cytometry (FCM) was used to determine the serum levels of T cell subgroups and immunoglobulins in 32 children with MPP at acute and recovery stages. Serum samples from 28 healthy children served as controls. RESULTS: The CD4 content (32.70±6.52/μL) and the ratio of CD4/CD8 (1.31±0.33) at acute stage in children with MPP were significantly lower that those in controls (40.15±4.49 /μL and 1.79±0.52, respectively) (P<0.01). Till to the recovery stage, the CD4 content (34.92±5.93/μL) and the ratio of CD4/CD8 (1.39±0.42) remained lower (P<0.01). There was no difference in the CD3 content between the MPP patients and controls at both the acute and recovery stages. The children with MPP showed higher serum concentrations of IgG (9.93±2.67 g/L) and IgM (1.73±0.83 g/L) at acute stage compared with the controls (8.01±2.47 g/L and 1.05±0.32 g/L respectively) (P<0.01). A significant difference for the serum concentrations of IgG and IgM was also observed at the recovery stage between MPP patients and controls. IgA content was not different between them. CONCLUSIONS: Immune function disturbance may exist in children with MPP. This study provides a basis for clinical application of immune regulators in the treatment of MPP.