Cocaine plasma levels and urinary excretion data from the literature were subjected to kinetic analysis. The objective was to present the available empirical data in a more useful form and provide a basis for interpretation of cocaine and/or metabolite concentrations in isolated urine samples. Cocaine disposition was modeled as a one-compartment open kinetic system exhibiting linearity within the usually encountered dose range. Model-predicted urine concentrations of cocaine, benzoylecgonine, and ecgonine methyl ester after a 100-mg cocaine dose were compared with literature values to test the validity of the model, and to indicate the use of ratios of concentrations in isolated urine samples to estimate the time since the dose of cocaine. A nomogram relating BZ urine concentrations to cocaine doses was constructed.