Several studies have suggested high predictive values of serum procalcitonin (PCT) for the discrimination of bacterial and viral meningitis in children and adults. Here, we report PCT serum concentrations in 12 adults suffering from bacterial meningitis. PCT on admission was normal ( < or = 500 pg/ml) in 3 and between 500 and 1,000 pg/ml in 2 patients without evidence of concurrent bacterial infections. Conversely, in 5 patients with PCT concentrations between 2,268 and 38,246 pg/ml other infections were present. PCT concentrations were higher with typical meningitis agents (pneumococci and meningococci 12,679 +/- 13,092 pg/ml vs. other bacteria 4048 +/- 9187 pg/ml, p = 0.041) whilst in nosocomial bacterial meningitis after neurosurgery (n = 3) serum PCT remained normal. We believe that PCT is of limited diagnostic value in adults suffering from bacterial meningitis, especially in cases due to unusual agents or of nosocomial origin. Elevated PCT in bacterial meningitis may indicate the presence of bacterial inflammation outside the central nervous system.