Chick embryo cells dissociated with trypsin reaggregate to a large measure within 24 hours. Addition of six volatile (chloroform, halothane, methoxyflurane, trichlorethylene, ether and nitrous oxide) and five nonvolatile (pentobarbital, thiopental, ketamine, chloralose and urethane) anesthetics to the cell suspensions inhibited reaggregation in a dose-related manner. The inhibitory action could be reverced by removal of the anesthetics. When anesthetics were added to the cells after aggregation, they were able to break up aggregates. Inhibition of aggregation was not produced by three local anesthetics, several central nervous system stimulants or depressants, some neurotransmitters (acetylcholine, serotonin, histamine) and their antagonists. The only non-anesthetic drugs found to inhibit aggregation was accelerated by catecholamines and GABA. A relationship of these observations to the mechanism of anesthetic action is suggested.