Changes in the activity of polyphenol oxidase (PPO) and in the levels of soluble sugars, soluble protein, total phenolic substances and ascorbic acid during the development and ripening of cherry laurel fruits were investigated. PPO activity and the other chemical constituents in the fruits harvested every week from the beginning of June to the mid July were spectrophotometrically analysed. PPO activity and phenolic content gradually increased during the development of the fruits, but decreased in the stage of ripening. Soluble sugar and soluble protein levels gradually increased, while the level of ascorbic acid decreased during fruit development and ripening. Polyacrylamide gel electrophoresis revealed quantitative changes in two PPO bands in the fruits.