Human butyrylcholinesterase (BChE, EC, 3.1.1.8) is capable of binding with organophosphate poisons and pesticides. Besides, it is able to catalyse the hydrolysis of many esters, peptides and amides. It is effective in prophylaxis or therapy of the intoxication of these compounds. Its structure study was made important progress by modeling and site-directed mutagenesis. It shed a light on the structure of peripheral anionic site of human BChE, and made the enzyme exhibiting organophosphorus acid anhydride hydrolase activity by amino acid substitution.