Abstract. The influence of coiling on column efficiency in capillary electrophoresis (CE) has been examined. In open tubular columns of 75-pm i.d., no significant effect of column coiling on efficiency was observed, even at plate counts of 2 x lo6 m-l. The small column internal diameter and radial diffusion in free solution was able to minimize the potential deleterious effect of coiling. With gel-filled columns of very high efficiency (-lo7 plates m-l), the influence of coiling on column efficiency was, however, significant, e.g., a factor of 3 or more loss in plate count per coil. For relatively rigid gels (e.g., 9 % T linear polyacrylamide with 7 M urea), this observed loss of column efficiency was attributed mainly to the inability of the polymer network to permit diffusional relaxation of the coiling effects. A significant influence of coiling on column efficiency was also found with medium concentration polymer networks (e.g., 3-6 % T linear polyacrylamide with no urea). The polymer network structure was assumed to change under the influence of mechanical stress caused by coiling, resulting in anisotropy across the column. Furthermore, the changes in structure and in efficiency were found to be time dependent and, in general, reversible. The effect appears to be caused by the shear force imposed on a polymer network structure, since changes are only observed when the column shape is altered after the polymer has been loaded into the capillary.