A method for the fast analysis of morphine (M), normorphine (NM), morphine-3- and -6-glucuronides (M3G and M6G) and codeine (C) is described which has the advantages of sensitivity, speed and specificity. Dihydrocodeine and heroin can also be assayed. The method is based on extraction of the opiates from serum, plasma and cerebrospinal fluid using reversed-phase solid-phase extraction columns, followed by reversed-phase high-performance liquid chromatography with native fluorescence detection. The extraction step provides greater than 95% recovery, and the response of the detection system is linear from 0.5 to beyond 750 ng. The method allows analysis of M, NM, M3G, M6G and C. No other drugs have been found to interfere with the assay. The assay offers a quick, cheap and reliable method of specifically determining morphine and its metabolites, including the potent M6G, from a small sample volume; this will be of advantage to both clinician and basic scientist.