Abstract In a previous paper (Nomura and Kurihara (1987) Biochemistry 26, 6135–6140), we demonstrated that the lipid bilayer membranes exhibit membrane potential changes in response to various odorants similarly to olfactory cells. The present study demonstrated that ion dependence of the responses of the lipid membranes to odorants is related to that in the carp olfactory system in the following point. (1) The responses to odorants diminished at low concentrations of salts and recovered upon addition of salts to stimulating solutions. (2) Divalent cations were effective in supporting the responses to odorants at much lower concentrations that monovalent cations. (3) Impermeable organic cations were effective in supporting the responses. The present results suggest that the initial process of generation of the receptor potential in olfactory cells resembles that in the lipid membranes.