Ion beams have increased usefulness for high-resolution microstructure fabrication if they are patterned to small dimensions before they strike a target. First, results are presented of maskless micromachining, doping, and resist exposure with a scanning focused gallium ion beam of sub-1000-Å diameter. Secondly, an ion-beam-transmission mask is described, and results are presented showing 1X replicated mask patterns with 0.6-μm features that were exposed in PMMA resist by irradiating the mask with a conventional size 150-kV proton beam. The potentials of ion-beam lithography using masks and focused ion beams are discussed.