To evaluate a possible association between varicella-zoster virus infection and glioma, the authors asked adults with glioma (n = 462) whose tumors were diagnosed between August 1, 1991, and March 31, 1994, and age-, sex-, and ethnicity-matched controls (n = 443) about their histories of chickenpox or shingles. Cases were significantly less likely than controls to report a history of either chickenpox (odds ratio = 0.4, 95% confidence interval (CI) 0.3-0.6) or shingles (odds ratio = 0.5, 95% CI 0.3-0.8). To obtain serologic support for these findings, the authors conducted double-blind enzyme-linked immunosorbent assays for immunoglobulin G antibodies to varicella-zoster virus among 167 self-reporting subjects for whom blood samples were available. Cases and controls reporting no history of chickenpox were equally likely to test positive (73% vs. 75%), but among those reporting a positive history, cases were less likely than were controls to test positive (71% vs. 85%). Despite the misclassification, an odds ratio of 0.6 was obtained using either serologic data (95% CI 0.3-1.3) or reported history of chickenpox (95% CI 0.3-1.1) in this subgroup of subjects. This suggests that adults with glioma were less likely than controls either to have had prior varicella-zoster virus infection or to have an immunoglobulin G antibody response adequate to indicate positivity. Since either explanation suggests novel mechanisms for brain tumor pathogenesis, these findings require corroboration and elaboration.