Epididymal fat pads from fasted rats, incubated in a medium of human albumin in Krebs Ringer phosphate buffer, served as test adipose tissue. Nor-adrenaline added to the medium considerably increased release of free fatty acids and glycerol; nicotinic acid, nicotinamide and nicotinuric acid had no effect. When 10-5 or 10-4 nicotinic acid or nicotinuric acid was added with noradrenaline, release of both glycerol and fatty acids was greatly reduced; nicotinamide had no effect. No explanation has been found for the blocking of the lipolysis induced by catecholamines, or the failure of nicotinamide to show any blocking effect.(For work in vivo see next Abst.) I. Leitch.