A polarization fluoroimmunoassay was developed for the detection of phencyclidine in urine and the reagents were adapted for use on the Abbott TDx analyser. The assay was used to look for evidence of phencyclidine abuse, over a 6 month period, amongst patients attending drug abuse clinics in the East End of London. Although over 2000 patients' samples tested negative, the assay successfully detected phencyclidine in an external quality control scheme.