Abstract Capillary liquid chromatography at moderately high pressures and capillary electrochromatography (CEC) have been combined to drive the mobile phase through capillary columns packed with small diameter particles. In a column packed with 1.5 μm nonporous particles, linear velocities near 3 mm/s were observed when combining inlet pressures of 690 bar (10,000 psi) and an applied voltage of 25 kV. Optimum linear velocity for the column was achieved using a pressure-voltage combination of 350 bar (5000 psi) and 5 kV. Separation efficiencies at near optimum linear velocity agreed with those predicted by the van Deemter equation for liquid chromatography. Retention factors were observed to decrease under pressure-voltage combination as the voltage was increased; such a behavior has been attributed to Joule heating effects.