CE in the presence of lipid bilayer disks was introduced as a new approach in membrane partitioning studies. The disks were used as a pseudostationary phase in the partial-filling mode of CE and the partitioning of cationic drugs was determined. The migration times of the analytes increased linearly with the lipid amount in the system. An appropriate algorithm for the calculation of a partition coefficient is presented. In the disk-shaped bilayers, which have excellent stability and shelf life, all of the lipids are readily available for interaction and the disks can be used as realistic cell membrane models.