A mass fragmentographic method for the quantitation of chlorpromazine (CPZ), mono-demethyl-chlorpromazine (nor1-CPZ), and 7-hydroxy-chlorpromazine (7-OH-CPZ) in plasma, cerebrospinal fluid, and tissues has been developed. The deuterated analogues of the compounds are used as internal standards. The high specificity was ascertained by multiple ion determination. The experimental error is below 10%. The sensitivity allows determination of sub ng quantities of CPZ per ml cerebrospinal fluid. The method has been applied to the analysis of drug concentrations in plasma and cerebrospinal fluid (CSF) of chlorpromazine-treated patients. The amount of CPZ in CSF was about 3% of the plasma level. The CPZ levels in plasma and CSF were significantly correlated.