Neutral macrocyclic alkali‐cation receptors have been covalently linked to one or more molecules of the membrane solvent 2‐nitrophenyl n‐octyl ether (NPOE). These compounds are all highly lipophilic and soluble in NPOE. The flux of alkali‐perchlorate salts through supported liquid membranes (SLMs) has been optimized by variation of the carrier content in the membrane and the temperature. With all carriers, the optimum flux is reached at carrier contents of about 20% (w/w) in NPOE. Above this carrier content the flux decreases because of an increase in the viscosity of the membrane solutions. Relatively low activation energies for transport indicate that the transport is diffusion‐limited. The excellent compatibility between the carriers and the membrane solvent leads to very stable membranes (NPOE/Accurel®). The mechanism of alkali perchlorate transport has been investigated by variation of the source‐phase salt activity and the carrier concentration. Indications about ion pair formation and 2/1 carrier/cation complexation have been obtained from variation of the carrier concentration and transport selectivity measurements.