1 The pharmacological properties of fatty acid amidohydrolase (FAAH) were investigated in brains of 35-day-old chickens, since nothing is known about the enzyme in avian species. 2 FAAH activity towards bothwas demonstrated in the chicken brains. The chicken FAAH was inhibited by the substrate analogues oleyl tri¯uoromethylketone (OTMK) and diazomethylarachidonyl ketone (DAK) with similar potencies to the rat FAAH. However, in contrast to the rat brain, phenylmethylsulphonyl¯uoride (PMSF) and the enantiomers of ibuprofen had very weak e ects on chicken brain FAAH. 3 Indomethacin and ni¯umic acid were found to inhibit rat brain AEA hydrolysis. The inhibition by indomethacin was reversible and competitive, with a K i value of 120 mM. Chicken FAAH was less sensitive to indomethacin than its rodent counterpart, but the inhibition was also competitive (K i ). 4 It is concluded that chicken FAAH activity has di erent pharmacological properties to its rodent counterpart.