We report magnetic and electrostatic phase imaging of micron-scale metallic lines covered with 525 nm of SiO 2 . Magnetic force microscopy (MFM) has been used to image a buried current-carrying line, to resolve its micron-scale defects, and characterize current crowding around those defects. The MFM phase signal from this structure compares quantitatively to the MFM signal from the same structure, taken prior to deposition of the oxide layer when transformed by a Green's function propagation to account for the oxide thickness. The alternative use of electric force microscopy (EFM) to find the location of a break and identify void defects in buried lines is contrasted with MFM. © 2003 Elsevier Science B.V. All rights reserved.