Numerous astrophysical objectives could be achieved with an astrometric instrument able to measure the angular separation of a pair of widely separated stars with an uncertainty of a few microarcseconds. An instrument that could make tens of measurements per day would form the basis for a multifarious scientific program. Although more complex, an astrometric interferometer offers a substantially larger information rate than a comparably-sized astrometric telescope for most applications. POINTS (Precision Optical INTerferometry in Space) is a design concept for an astrometric interferometer originally conceived as a means of performing the light deflection experiment of general relativity to second order. The present "strawman" version, which has a pair of 2 m baselines and four 25 cm telescopes, would fit fully assembled with a support spacecraft in one-third of the Shuttle bay. For a pair of tenth-magnitude stars about 90° apart, POINTS would yield the separation uncertain by 5 μas after a 10-minute observation. We consider both the design of the instrument and aspects of a mission.