A lubrication theory that includes the effects of electric double layer (EDL) and boundary slip is developed. Both effects are important in microflow, and thus in lubrication problems. They have opposite effects on velocity distributions between lubricating surfaces. Also, the velocity distribution induced by the EDL stream potential (electroviscous effect) is affected by the boundary slip. Under the usual assumptions of lubrication and Debye-Hückel approximation for low surface potential, the Navier-Stokes equation with body force due to the electrical potential as well as the widely accepted Navier slip boundary conditions is utilized on deriving the modified Reynolds equation. Effects of EDL and boundary slip on the 1-D bearing performance are discussed by solving the modified Reynolds equation numerically.