Synchrotron x-ray fluorescence experiments were performed using a prototype undulator for the Advanced Photon Source installed on the CESR storage ring at Cornell University during a run in May, 1988. Fluorescence spectra were collected from a number of standard references and unknowns. Thick target minimum detectable limits (MDL) were about a factor of two higher than those obtained using white bending magnet radiation at the NSLS. The higher MDLs could be due to lower polarization and/or imperfect alignment of the Si(Li) detector. Thin target MDLs were about 10 times lower than the NSLS since the undulator produced a usable spot size which was also 10 times smaller. Several one dimensional multi-elemental scans and two dimensional images were made with 10 μm resolution and 30 ppm MDL. These experiments demonstrate that undulators on the proposed Advanced Photon Source will be ideal for a trace element x-ray fluorescence microprobe with excellent elemental sensitivity and spatial resolution.