In this paper, we explore the multiphoton excitation capabilities of the scanning total internal reflection fluorescence microscopy (STIRFM) using a focused ring-beam illumination and a high numerical-aperture objective (NA = 1.65). The evanescent field produced by the STIRFM is focused laterally, producing a small excitation volume that can effectively induce non-linear optical process. The theoretical simulation of the focal spot produced in STIRFM geometry shows that the focused evanescent field is split into two peaks due to the strong enhancement of longitudinal polarization component at the focus of a high numerical-aperture objective. Experimental images of two-photon excited CdSe quantum dot nanocrystals show the characteristic split focal spot.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.