To ascertain an overdose, pathologists must be able to unequivocally identify the drug and determine a reliable blood concentration. The approach used here combined a standard addition technique and three different chromatographic techniques, i.e., high performance liquid chromatography (HPLC), high performance thin-layer chromatography (HP-TLC), and gas chromatography/mass spectrometry (GC/MS). Each type of chromatography was carried out on the same extract by splitting the residue in thirds. HLPC provided a quantitative result of 1.2 mg/L in blood; this result was confirmed by quantitative data derived from HP-TLC and GC/MS. In addition, these techniques provided information about two metabolites (nordoxylamine and dinordoxylamine) and conclusive identification. Blood nordoxylamine was 0.52 mg/L and doxylamine plus metabolites in urine was 25 mg/L. 5 tables, 3 figures, and 6 references