An earlier study that showed the importance of cerebrospinal fluid polyamine levels for monitoring patients harboring medulloblastomas was expanded to 210 determinations evaluated in 32 patients. The results and conclusions of our earlier study have been confirmed in this expanded patient group. Patient status, with regard to either progression or regression of tumor, was determined by correlating polyamine levels with neurologic examination, computerized tomography, radionuclide scan, cerebrospinal fluid cytology, and myelography. The polyamine assay was predictive of recurrence in 15 patients; three false negatives and no false positives were found. We feel that cerebrospinal fluid polyamine determinations should be a routine diagnostic procedure in the long-term monitoring of patients harboring medulloblastoma.