Neoplastic meningitis (NM) occurs in approximately 8% of all cancer patients. To confirm a clinical impression that NM is relatively common in patients who undergo surgical resection of an isolated cerebellar metastasis (ICM), a retrospective study was performed. All patients who underwent a surgical resection of an isolated CNS metastasis at The Johns Hopkins Hospital between January 1991 and June 1993 were identified. Their charts, laboratory and pathologic data, radiologic studies, survival and cause of death were reviewed. A total of 66 patients were identified fifty-five patients underwent a surgical resection of a supratentorial metastasis while 11 patients (6 females and 5 males) underwent a surgical resection of an isolated cerebellar metastasis. The ages of patients with cerebellar metastases ranged from 23 to 74 years at the time of diagnosis with a median age of 49 years. All 11 patients had stable systemic disease and an excellent performance status. Five patients had tumors from lung, 2 from breast, and 4 from other sites. Each was expected to have a long survival. However, 4 of the 11 patients (36%) developed unequivocal NM at 1, 3, 6, and 7 months following surgical resection and all died within 1 month from the diagnosis of NM. Two patients had a positive CSF cytology and the other two had multiple enhancing leptomeningeal metastases on MRI. Two additional patients died of progressive neurological disease without evidence of local recurrence, yet were never formally evaluated for NM and two were lost to follow-up. Thus, the incidence of NM in this patient population is at least 36%. In the 55 patients who had resections of supratentorial metastases, only 1 patient (2%) developed NM. This study suggests that NM following surgical resection of an ICM may be common and may result in the premature demise of patients with excellent performance status, minimal systemic disease, and a reasonable life expectancy. Further studies are needed to determine if prophylactic intrathecal chemotherapy administered perioperatively could diminish the incidence of clinically apparent NM in this patient population.