Toxicological analysis for chlorpromazine and diazepam was performed using chemically fixed organ tissue specimens. After chlorpromazine and diazepam had been injected into rabbits, organ tissues (brain, lung, liver, kidney and skeletal muscle) were collected and fixed in 3 fixative solutions: buffered 10% formalin solution (pH 7.4, 10% BF), non-buffered 10% formalin solution (pH 5.1, 10% non-BF), buffered 4% paraformaldehyde solution (pH 7.4, 4% BPA). Chlorpromazine and diazepam were determined by GC-MS (gas chromatography-mass spectrometry) after 5 different fixation periods, and were detected even after 28 days of fixation. Recoveries of chlorpromazine and diazepam in 10% BF were within the range 48-86% and 68-171%, respectively after 28-day fixation, those in 10% non-BF were 22-54% and 48-78%, respectively, and those in 4% BPA solution were 13-59% and 14-50%, respectively. Thus, 10% BF was found to be the most suitable fixation medium for analysis of chlorpromazine and diazepam.