Two male patients with high-grade gliomas were treated with subtotal or total resection and radiotherapy followed by a lomustine-containing chemotherapy regimen. Both patients took lomustine at an oral dose of 800 mg over five days instead of their regular doses of 200 and 240 mg. Grade 4 neutropenia and thrombocytopenia developed in both patients within two weeks of the last lomustine dose. One of them was admitted to hospital because of febrile neutropenia. Neutropenia and thrombocytopenia were detected in the other patient when he was examined in the emergency room following a generalized convulsion. Both patients recovered from the severe myelosuppression caused by lomustine. No other organ toxicities were observed.