The concentrations of 3-beta-hydroxybutyrate (3HB) in femoral blood, urine, vitreous humor as well as pericardial and cerebrospinal fluids were retrospectively examined in a series of medico-legal autopsies, which included cases of diabetic ketoacidosis, hypothermia fatalities without ethanol in blood, bodies presenting mild decompositional changes, and sudden deaths in chronic alcoholics. Similar increases in 3HB concentrations were observed in blood, vitreous, and pericardial fluid, irrespective of the cause of death, suggesting that pericardial fluid and vitreous can both be used as alternatives to blood for postmortem 3HB determination. Urine 3HB levels were higher than blood values in most cases. Cerebrospinal fluid 3HB levels were generally lower than concentrations in blood and proved to be diagnostic of underlying metabolic disturbances only when significant increases occurred.