The role of transient effects and advective transport of species has been investigated for scanning electrochemical microscopy (SECM) in the context of a frame electrode integrated with an atomic force microscope (AFM) probe. Numerical simulations indicate that for mass diffusion Peclet numbers corresponding to typical diffusivities, length scales and velocity scales (Pe <= 0.1), the use of a steady-state diffusion model for species transport to SECM electrodes is appropriate. Some experiments could fall outside this regime, and it is therefore necessary to carefully determine appropriate length and velocity scales on a case-by-case basis. We also present original additions to frame electrode theory and the use of the boundary element method in numerical simulation of SECM. (c) 2005 Elsevier B.V. All rights reserved.