Benzodiazepine (lorazepam, estazolam, chlordiazepoxide, and ketazolam) stability was studied in postmortem blood, bile, and vitreous humor stored at different temperatures over six months. The influence of NaF, in blood and bile samples, was also investigated. A solid-phase extraction technique was used on all the studied samples, and benzodiazepine quantification was performed by high-performance liquid chromatography-diode-array detection. Benzodiazepine concentration remained almost stable in all samples stored at -20°C and -80°C. Estazolam appeared to be a stable benzodiazepine during the six-month study, and ketazolam proved to be the most unstable benzodiazepine. A 100% loss of ketazolam occurred in all samples stored over 1 or 2 weeks at room temperature and over 8 or 12 weeks at 4°C, with the simultaneous detection of diazepam. Chlordiazepoxide suffered complete degradation in all samples, except preserved bile samples, stored at room temperature. Samples stored at 4°C for 6 months had a 29-100% decrease in chlordiazepoxide concentration. The data obtained suggest that results from samples with these benzodiazepines stored long-term should be cautiously interpreted. Bile and vitreous humor proved to be the most advantageous samples in cases where degradation of benzodiazepines by microorganisms may occur.