The influence of experimental conditions on gradient high-performance liquid chromatography/diode array detector separation and identification of 13 psychotropic drugs belonging to two groups--phenothiazines and tricyclic antidepressants--was examined. The main interaction effects of three experimental factors were determined according to a 2 3 factorial design, and the optimum conditions of analysis were searched for. The degree to which the chromatographic peaks overlap is taken into account in a proposed criterion for separation quality. The screening analysis proposed was tested on whole blood samples spiked with mixtures of the examined drugs. The method was characterized by such validation parameters as relative retention times, absorbance ratios at two wavelengths, detection limits, linearity ranges, and extraction recoveries. The method proved to be a suitable tool for the identification of psychotropic drugs tested for forensic purposes.