Any chromatographic analysis of urine for cocaine requires the use of an efficient extraction procedure, together with a sensitive analytical technique. Column switching has been previously reported to be useful for the preliminary identification of drugs in biological samples such as plasma and vitreous humor. This approach involves the use of a precolumn placed in the injection loop of the high-performance liquid chromatograph in such a way that a sample can be injected onto the precolumn and then flushed with another solvent. The precolumn retains the compounds of interest while the endogenous compounds run to waste. The sample can then be washed by injecting, typically, 0.5 to 1 mL of water, buffer, or organic solvent through the injection system. After flushing, the injector is switched to the inject position, and the mobile phase passes through the precolumn and takes the relatively pure compounds of interest onto the analytical column. This technique eliminates lengthy extraction procedures prior to the chromatographic analysis. The method was used to screen postmortem urine samples for the presence of cocaine and benzoylecgonine. Recoveries of near 100 percent make this an attractive technique for the analysis of very low drug concentrations. The volume of urine injected onto the system can also be increased up to 2 mL, thus concentrating the sample onto the precolumn as an additional step to improve sensitivity. 2 figures and 6 references