[35S]Lanthionine ketimine binds specifically and with high affinity to bovine brain membranes. This binding has been studied in detail. It is reversible, not occurring at an uptake site or at a metabolizing enzyme and depending only weakly from ionic strength; it is affected by thiol reagents. [35S]Lanthionine ketimine specific binding is displaced only by other ketimines and by catecholamines, but not by more selective adrenergic ligands; binding parameters are reported. [3H]Adrenaline but not [3H]dihydroalprenolol is partially displaced by lanthionine ketimine. With bovine brain preparations a significant stimulation of basal adenylate cyclase activity by lanthionine ketimine is observed.