We have developed a rapid test for the detection of morphine and its metabolites in urine by adsorption on cation-exchange resin-coated plastic rods. The method is sufficiently specific to differentiate morphine from synthetic opiates such as pethidine. The sensitivity of this method is down to 1.0 microgram/ml for morphine and 0.1 microgram/ml for pethidine, being similar to that of the thin-layer chromatographic (TLC) method and superior to some screening kit procedures. Our method makes it possible and easy to detect opiates in urine samples on the spot and to easily transport the coated rods to the laboratory for subsequent analysis. The sensitivity, specificity and validity of the method were examined and compared with those of the TLC and radio-immunoassay (RIA) procedures.