Micromolding techniques for the fabrication of polymer microstructures are discussed with reference to the features important for commercial success. Particular emphasis is placed on a recently developed photopolymerization reaction injection molding (RIM) technique. The progress made to date on the molding of microstructures using this technique is detailed and compared with thermally initiated RIM. The goal is to fabricate structures with lateral dimensions in the micrometer range, structural details in the submicrometer range, and high aspect ratios.