Cerebral lymphoma is usually identified on computed tomographic/magnetic resonance scan as a homogeneously contrast-enhancing periventricular mass lesion. We present 10 patients with cerebral lymphoma who had nonenhancing tumor on computed tomographic (2 patients) or magnetic resonance scan (8 patients) either at the time of diagnosis or recurrence. The absence of enhancement caused diagnostic delay in all patients and suggests that tumor resides behind an intact blood-brain barrier, raising important therapeutic implications in the design of chemotherapeutic regimens.