Nimustine (ACNU) has antitumor activities in patients with malignant glioma. Hyperbaric oxygen (HBO) may enhance the efficacy of certain therapies that are hampered by the hypoxic microenvironment. We examined the combined effects of ACNU and HBO in a GFP transgenic nude mice bearing human glioma model. Mice inoculated with human glioma cells SU3 were randomly divided into the four groups: (A) the control group, (B) the HBOT (HBO therapy) group, (C) the ACNU group, and (D) the HBOT+ ACNU group. Tumor size was measured at the indicated time intervals with a caliper; mice were sacrificed 28 days after treatment, and immunohistochemistry staining and western blot analysis were carried out. By the end of the trial, the tumor weights of groups A, B, C, and D were (P < 0.05), 6.03 +/- 1.47, 4.13 +/- 1.82 (P < 0.05), 2.39 +/- 0.25 (P < 0.05), and 1.43 +/- 0.38 (P < 0.01), respectively. The expressions of TNF-alpha, MMP9, HIF-alpha, VEGF, NF-kappa B, and IL-1 beta were associated with the infiltration of inflammatory cells and the inhibition rate of tumor cells. Hyperbaric oxygen therapy (HBOT) could inhibit glioma cell proliferation and inflammatory cell infiltration, and exert a sensitizing effect on ACNU therapy partially through enhancing oxygen pressure (PO2) in tumor tissues and lower expression levels of HIF-1 alpha, TNF-alpha, IL-1 beta, VEGF, MMP9, and NF-kappa B.