The purpose of the present study was to investigate the effect of anaerobic exercise on aspects of cellular immune function among 10-12-year- old highly trained female gymnasts (n = 7) compared with age- and maturity- matched untrained girls (n = 6). Blood samples were drawn before, immediately after, and 24 hr following exercise. Leukocyte number, particularly neutrophils and lymphocytes, increased following 30 s of supramaximal exercise and returned to baseline values following 24 hr in both groups. Total T-cell and B-cell concentrations, as well as T-helper (CD4) and T- suppressor (CD8) number increased immediately after exercise and decreased following 24 hr in both groups. The CD4:CD8 ratio was reduced following exercise mainly due to an increase in CD8. Natural killer cell count was elevated following exercise and continued to be elevated 24 hr following exercise in both groups. In summary, the exercise-induced changes in cellular immune function among both groups were similar to changes described in adults.