The synthesis of "Janus" particles (whose hemispheres are physically or chemically different) is of growing importance for the development of novel materials, but the behavior of such particles in external fields has not been studied in depth. The application of AC electric fields in aqueous suspensions of anisotropic particles leads to unbalanced liquid flows and nonlinear, induced-charge electrophoretic (ICEP) motion. We report experimental observations of the motion of "Janus" microparticles with one dielectric and one metal-coated hemisphere induced by uniform fields of frequency 100 Hz - 10 kHz in NaCl solutions. The motion is perpendicular to the field axis and persists after particles are attracted to a glass wall. The velocity as a function of field strength, AC frequency and particle size are consistent with ICEP theory in dilute solutions (≤ 100 μM), but we observe anomalous behavior at higher concentrations, including no motion above 10 mM. This phenomenon may find applications in microactuators, microsensors, and microfluidic devices.