The local immune response to echovirus 30 meningitis in children was investigated in 2 ways: using Row cytometry to examine the mononuclear cell and lymphocyte subsets and enzyme-linked immunosorbent assays to examine the cerebrospinal fluid (CSF) levels of cytokines, including monocyte chemoattractant protein-1 (MCP-1), interferon gamma (IFN-gamma) and interleukin-12 (IL-12), The numbers of macrophages in the CSF were increased, in particular during the early part of the acute stage. The levels of MCP-I, which is responsible for the accumulation of macrophages, as well as those of IFN-gamma and IL-12, which play important roles in the activation of macrophages and T helper (Th) 1 cells, respectively, were increased in the CSF of patients compared with the levels found in the controls. Likewise, numbers of activated CD4+ and CD8+ T lymphocytes mere increased in the CSF, Since the ratio of CD4/CD8 correlated with the age of the patients, CD8+ lymphocytes in the CSF might play a more important role in younger children.