Neuron-specific enolase (NSE) activities were measured in cerebrospinal fluid (CSF) in 361 patients with various neurological diseases. CSF was collected as part of the diagnostic procedure both in the control group, which consisted of 189 subjects with low back pain, and in the patient group (172 patients). The mean CSF NSE level in 189 control subjects was 7.14 +/- 1.94 micrograms/l. Slight elevations of CSF NSE (> or = 11.0 micrograms/l) were observed in 9 patients with non-malignant diseases and in 2 patients with malignant diseases. The findings of this study indicate that measurement of NSE in CSF cannot be used as an adjunctive diagnostic test for CNS metastases.