[Serum quantitative C-reactive protein concentrations were measured in 186 patients admitted with suspected neuroinfection or symptoms of other diseases in the central nervous system. The diagnoses were purulent meningitis (102), abscessus cerebri (5), meningitis basilaris (2), meningitis cryptococcica (1), sepsis (11), encephalitis (22), encephalopathia (5), autoimmune central nervous illness/disease/disorder (22), non-inflammatory central nervous disease/ disorder (12) and tumour cerebri (4). The highest values of C-reactive protein were measured in patients suffering from abscessus cerebri (250.8 +/ 64.2 mg/l), sepsis (221 +/- 16.4 mg/l) and purulent meningitis (153.0 +/- 94.59 mg/l). Serum C-reactive protein concentrations were moderately increased in viral infections (36.8 +/- 36 mg/l). The C-reactive protein level in the normal range in patients suffering from non-inflammatory and autoimmune central nervous illnesses/diseases/ disorders (4.0 +/- 1.5 mg/l or 10.0 +/- 18.5 mg/l). During our examinations the C-reactive protein levels showed both local and septicaemic reactions. C-reactive protein is considered as a valuable laboratory parameter both in diagnosings central nervous system diseases with suspected bacterial infection and in monitoring therapeutic efficiency.]