In this paper, near-wall electrophoretic motion of spherical particles in cylindrical capillaries was experimentally investigated. It is demonstrated that same-sized particles move faster in smaller capillaries. This observation verifies the theoretical prediction of the wall enhancing effect in our recent paper (C. Ye, X. Xuan, D. Li, Microfluid. Nanofluid. 1 (2005)). Our experiments show that this wall enhancing effect becomes more significant when the size difference between particle and capillary becomes smaller and when a dilute electrolyte solution (i.e., thicker electric double layer) is used. (c) 2005 Elsevier Inc. All rights reserved.