An evaluation of the validity of postmortem chemical studies from body fluids requires determining when the specimen was obtained, the source of the fluid and method of removal, the analytical methodology and normal values, and variations of vitreous humor levels in different eyes. A discussion of carbohydrates in the human body addresses glucose and lactic acid, and a discussion of nitrogenous compounds focuses on urea and creatinine, other nitrogenous compounds, and oxypurines. The section on electrolytes considers sodium and chloride; potassium; calcium, magnesium, phosphorus, and sulphur; and other trace metals. Other sections discuss lipids, proteins, immunology, bile pigments, enzymes, and hormones. Vitreous studies of glucose, urea, sodium, chloride, and other chemical parameters provide medical information that can expose disease conditions such as diabetes mellitus, uremia, and various types of electrolyte imbalance. Potassium measurement in the vitreous is the most reliable chemical test for estimating the time of death in the majority of cases. Hormone analyses, enzyme studies, and protein measurements may assist in confirming the presence of some diseases and in detecting additional diseases as well as other causes of death. A forensic pathologist must be schooled in postmortem changes in the body's chemical substances and also be proficient in procedures that provide accurate results in a given situation. 2 tables, 2 figures, and 210 references