The study was performed to evaluate the levels of some enzymes (AST, ALT, HGTP, LDG) and free amino acids (aspartic, glutaminic, glycine, isoleucine, leucine) in liquor of 37 subjects who got poisoned with a Malathion insecticide. Their condition was diagnosed as moderate and severe. The liquor was obtained on poisoning day 1, 3, 10, 14 and 21. The liquor levels of enhancement mediatory amino acids, aspartic and glutaminic, rise early in poisoning, while concentration of inhibition mediator glycine tends to decline. Progress of intoxication brings about a rise in LDG and GGTP activity attributed to a membranotoxic effect of the insecticide.