Cetiedil is a potent blocker of acetylcholine and choline fluxes. Several analogs of this compound have been synthesized and their effect on acetylcholine (ACh) and choline fluxes in synaptosomes and on ACh uptake in synaptic vesicles have been studied. The effects of these analogs were compared to those of other drugs acting on cholinergic functions. All these compounds were also studied in relation to the ACh translocating properties of the mediatophore, a protein recently purified from cholinergic nerve membranes and probably involved in the final step of release. We thus obtained a pattern of drug action for the three functions under study. The patterns of drug action on ACh release from synaptosomes or proteoliposomes were similar and clearly different from those for either synaptosomal choline transport or vesicular ACh uptake. In addition, the main outlines of the structure-function relationship for each of the functions studied, are described for cetiedil analogs.