The ripening of avocado (Persea americana Mill.) fruit slices was inhibited whether they were floated in water or in buffered aqueous 0.3 m mannitol, 0.25 m KCl, and sucrose. There was no evidence to support the contention that ripening occurred when the tonicity of the bathing medium was increased. Decreased gaseous exchange is considered to be a major cause of this inhibition because by utilizing a technique that afforded better aeration, slices could be water infiltrated and still ripen normally. Metabolic studies on the ripening of slices using this method indicated that several metabolic inhibitors, malonate, cyanide, acetaldehyde, dinitrophenol, and fluoride did not prevent ripening, but that their effect on the respiration pattern was marked. This technique provides a suitable way to study control of ripening at the tissue level.