The role of amiloride in the labellar responses to various taste stimuli in the blowfly Protophormia terraenovae was studied with the aim of ascertaining whether amiloride-sensitive cation conductances are present in the chemosensory systems of insects. Results include that: 1) amiloride has no effect on the "salt" cell response to any stimulus; 2) amiloride decreases the "sugar" cell response to fructose, but does not affect that to sucrose; 3) the effects of amiloride on the responses of the "water" cell and the "fifth" cell are less clearly definable, due to the probable superimposition of osmotic mechanisms in the former and the poorly known response modalities of the water. In conclusion, amiloride-sensitive receptor sites seem to exist also in insects. However, unlike most vertebrates investigated, they are principally located in the sugar receptor cell, not on the salt cell.