During studies on the relationship between central biogenic amines and tolerance and physical dependence on morphine, we found that the widely used fluorometric assay for the estimation of brain amines has a number of defects. Some of these were high background values and lack of suitable controls for interfering substances in brain tissue. We therefore developed a set of new assays for the biogenic amines, dopamine, norepinephrine, 5-HT, 5-HIAA and acetylcholine. Using a system consisting of combined gas chromatograph mass spectrometer computeriz, these methods corrected several troublesome points in the fluorometric assays. Part 1 describes the gas chromatograph assays for dopamine, norepinephrine, 5-HT and 5-HIAA and it's use to study the role of biogenic amines in physical dependence of mice on morphine.