Abstract Pluto is the last known planet in our Solar System awaiting spacecraft reconnaissance. In its eccentric orbit taking it 50 AU from the Sun, Pluto presently has a thin atmosphere containing methane, which is projected to “collapse” back to the icy planet's surface in about three decades, following Pluto's 1989 perihelion pass at 30 AU. Based on ground and Earth-orbit-based observing capabilities limited by Pluto's small size and extreme distance, present top-priority scientific questions for the first mission concern Pluto and Charon's surface geology, morphology and composition, and Pluto's neutral atmosphere composition. Budgetary realities preclude a large, many-instrument flyby spacecraft, while distance and launch energy requirements preclude any but the smallest orbiter using presently available launch vehicles and propulsion techniques. A NASA-sponsored Pluto Mission Development activity began this year. Two alternative cost-constrained mission implementations are described, based on which a primary implementation will be chosen. The Pluto Fast Flyby (PFF) mission utilizes an 83 kg (dry) spacecraft launched in 1998 aboard a Titan IV(SRMU)/Centaur for an ∼7 year direct trajectory to Pluto. Instruments described are an integrated CCD-imaging/ultraviolet spectrometer, with a possible integrated infrared spectrometer. The larger Pluto-350 spacecraft, ∼316 kg, carries a broader instrument set, greater redundancy, and requires > 11 year flight time launching in 2001 aboard a Delta or Atlas, toward Earth and Jupiter swingbys to provide the energy to reach Pluto. Launch by Proton is under consideration. Both mission implementations store data during the brief encounter, to be played back over several months. Cost is the primary design driver of both alternatives, with major tradeoffs between spacecraft development, launch services, radioisotope thermoelectric generator procurement and launch approval, and mission operations. Significant benefits are apparent from incorporating “microspacecraft” technologies from Earth orbiters.