The Army Aviation and Missile Research, Development, and Engineering Center (AMRDEC) initiated a research and development project several years ago to develop Micro Electro-Mechanical Systems (MEMS)-based phased arrays to provide rapid beam steering for sensors, optical and Radio Frequency (R-F) missile seekers, and RF communication links. In particular, the joint AMRDEC/Army Research Laboratory (ARL) project, which leverages low-cost phased array components developed under the Defense Advanced Research Projects Agency (DARPA) Low Cost Cruise Missile Defense (LCCMD) project, is developing RF switches, phase shifters, and passive phased sub-arrays to provide a fast scanning capability for pointing, acquisition, tracking, and data communication; and rugged, optical MEMS-based phased arrays to be employed in small volume, low-cost Laser Detection and Ranging (LADAR) seekers. The current status of the project is disclosed in this paper. Critical technical challenges, which include design and fabrication of the RE switches and phase shifters, design and fabrication of micro lens arrays, control of beam steering, scanning angular resolution and array losses, are discussed. Our approach to overcoming the technical barriers and achieving required performance is also discussed. Finally, the validity of a MEMS technology approach against competing low cost technologies is presented.