G207, a mutant herpes simplex virus (HSV) type 1, is safe when inoculated into recurrent malignant glioma. We conducted a phase 1 trial of G207 to demonstrate the safety of stereotactic intratumoral administration when given 24 hours prior to a single 5 Gy radiation dose in patients with recurrent malignant glioma. Nine patients with progressive, recurrent malignant glioma despite standard therapy were included. Patients received one dose of G207 stereotactically inoculated into the multiple sites of the enhancing tumor margin and were then treated focally with 5 Gy radiation. Treatment was well tolerated, and no patient developed HSV encephalitis. The median interval between initial diagnosis and G207 inoculation was 18 months (mean: 23 months; range: 11-51 months). Six of the nine patients had stable disease or partial response for at least one time point. Three instances of marked radiographic response to treatment occurred. The median survival time from G207 inoculation until death was 7.5 months (95% confidence interval: 3.0-12.7). In conclusion, this study showed the safety and the potential for clinical response of single-dose oncolytic HSV therapy augmented with radiation in the treatment of malignant glioma patients. Additional studies with oncolytic HSV such as G207 in the treatment of human glioma are recommended. © 2014 The American Society of Gene and Cell Therapy.