A new scanning near-field optical microscopy based on the surface plasmon resonance is presented. Enhanced fields are localized at individual surface irregularities by the scattering of plasmons and the scattered plasmons produce a conical radiation. Variations in the conical radiation intensity caused by interactions between a raster-scanned probe tip and the enhanced fields are recorded and related to the surface topography, providing an optical image with lateral resolution exceeding the diffraction limit. This technique is compared to complementary atomic force microscopy and scanning tunneling microscopy measurements and potential advantages are discussed.