Based on postmortem toxicological analysis, there was just over a 10-fold increase in methadone fatalities in Kentucky between 2000 and 2003, increasing from 6 cases in 2000 to 68 cases in 2003. Of the 176 methadone-related deaths, methadone was the only drug detected in postmortem blood and urine toxicological analyses in 11 cases (6.25 percent). The mean methadone blood concentration in all 176 cases was 0.535 mg/L (0.02-4.0). The psychoactive medications detected were antidepressants (39.8 percent), benzodiazepines (32.4 percent), and other opioids in addition to methadone (27.8 percent). Cannabinoids were found in 44 cases (28.4 percent). Cocaine or metabolite was present in 34 cases (21.9 percent). Of the 95 individuals with a known history of methadone use, 46 (48.4 percent) involved a prescription by a private physician. The authors advise that the interpretation of blood methadone concentrations alone or combined with other psychoactive drugs requires attention to the subject's potential chronic use of and tolerance to the drug. An investigation of procurement practices and the use/abuse of methadone were required before the cause of death can be determined. In the current study, the coroner of each jurisdiction supplied pertinent drug history on the cases, particularly methadone acquisition and use. The coroner also documented medical history, including treatment for chronic pain. In each autopsy, the age, race, sex, and body mass index of the victim was recorded. Chart review substantiated all blood and urine toxicological findings. Evaluation of tolerance included consideration of the history of past exposure, including amount, frequency, and duration of consumption. 6 tables, 1 figure, and 33 references