A 46-year-old woman with non-Hodgkin's lymphoma presented with a new onset of seizures. A cranial CT was interpreted as normal. Eight months later, she presented with changed mental status and leg weakness, and a repeat CT scan showed multiple ring-enhancing lesions close to the left frontal sinus, with mass effect. A review of the previous CT scan showed a very small area of sinusitis as well as a small ring-enhancing lesion contiguous to it. A short course of intravenous steroids markedly relieved her symptoms, and a stereotactic biopsy confirmed Aspergillus fumigatus to be the cause of the infection. She was successfully treated with Amphotericin B. Central nervous system (CNS) aspergillosis is a potentially fatal disease. The therapeutic success in this case was related to a high index of suspicion at her second presentation. As the early signs of infection might be subtle and easily missed, patients at high risk for opportunistic infection should be studied carefully when new onset of CNS symptoms occur. Early initiation of therapy should improve the prognosis in such cases.