A GLC analysis is presented for loxapine, amoxapine, and their major metabolites in serum and urine. Electron-capture detection is employed for serum analysis, and flame ionization is used for urine analysis. The procedure includes trifluoroacetylation of secondary amine functions, followed by trimethylsilylation of phenolic groups after ethyl acetate extraction of the sample. Urine requires prior enzymatic hydrolysis of conjugates. Data indicating the utility of the procedure in hospitalized patients and normal volunteers are presented.