A GC method has been developed for the simultaneous determination of catecholamines, simple tetrahydroisoquinolines, a complex benzyltetrahydroisoquinoline alkaloid as well as the phenanthrene (opium) alkaloids. These chemical classes of pharamcologically active bases were separated and identified as trimethylsilylether derivatives on a six ft, 3% OV-1 column. Morphine, normorphine, and codeine were completely separated from each other as well as from their biosynthetic precursor in the opium poppy, tetrahydropapaveroline (THP). Additionally, THP is a known alkaloid metabolite of the neuroamine, dopamine, in animal systems. By this procedure dopamine, its O-methylated metabolite 3-methoxytyramine, a simple isoquinoline alkaloid derivative of dopamine formed by condensation with acetaldehyde salsolinol, and THP, as well as the narcotic alkaloids could be analyzed on a single sample. This method should be of general applicability to several diverse biomedical problems. GLC analysis of these compounds would be useful in such areas as alkaloid metabolism in plant and mammalian systems, drug abuse detection, biogenic amine metabolic pathway studies, investigations involving the interaction of narcotic alkaloids with neurotransmitter stores, and especially in alcoholism research concerning the interaction of alcohol with neuroamine metabolism.