VIP, glucagon or several other neuropeptides were applied to intact retinae in vitro. VIP was found to be a very potent stimulator of cyclic AMP production in rabbit retina, whereas glucagon was efficient in pigeon retina. Attempts to modify the VIP-induced formation of cyclic AMP by somatostatin or dopamine-related drugs (neuroleptics) were not successful. These biochemical data may be correlated to some extent with the recent immunohistochemical localisation of VIP and glucagon in mammalian or avian retinae.