Abstract We used gas chromatography in conjunction with flame ionization detection to quantitative nine polyls and aldo and keto sugars (as silyl derivatives) in human plasma and cerebrospinal fluid (CSF). Rhamnose, not found in CSF or plasman, was used as an internal standard with a lower limit of quantitation of 0.4 mg/l. CSF polyol and sugar concentrations (mean ± S.D.) in fourteen healthy subjects (age range 27.1-85.9 years) were: anhydroglucitol, 19.9 ±5.3 mg/l;arabitol, 4.8±0.9 mg/l; erythritol, 2.4±0.5 mg/l; myoinositol, 29.6±8.3 mg/l; ribitol, 1.6±0.1 mg/l; fructose, 25.5±11.1 mg/l;glucose, 587±70 mg/l;glucitol, 7.7±1.5 mg/l;and mannose, 10.6±2.4 mg/l. The respective plasma concentrations were 30.6±11.5, <0.4, 0.4±0.2, 6.3±2.6, <0.4, 23.4±21.4, 897±214, <0.4 and 13.7±6.3 mg/l. Polyol CSF-to-plasma concentration ratios greater than 2 were observed for myoinositol, erythritol, arabitol, glucitol and ribitol, indicative of active accumulation or synthesis of these polyols within the central nervous system.