MX2, a new lipophilic morpholino anthracycline, has been reported to have superior chemotherapeutic effects to adriamycin against murine and human tumor cells. In this study the chemotherapeutic effect of MX2 against C6 glioma cells was examined as well as the photocytotoxicity of MX2 and the combination effect of MX2 and photodynamic therapy (PDT) in vitro. Colony formation is inhibited even with only 2 hour treatment with MX2 in a dose-dependent manner. In this colony forming efficiency assay the drug concentration required for 50% inhibition of colony formation for C6 glioma cells was 24.0 +/- 4.5 ng/ml. Mild photocytotoxicity of MX2 against C6 glioma cells was observed at a high concentration (100 ng/ml) of MX2 following exposure to white light but not red light. In combination, MX2 and the photosensitizer haematoporphyrin derivative (HpD) exhibited an additive cytotoxic effect against C6 glioma cells when the cells were treated with MX2 either immediately after red light illumination following incubation with HpD or at an interval of 24 hours before incubation with HpD. We conclude that MX2 may be clinically useful against malignant glioma alone, and in combination with other therapies such as PDT.