The concept of microfission, whereby a small target of fissile material is burned under compression, was introduced nearly 20 years ago; the size of the target is limited by the magnitude of the compression and by the initial number of fissions that start the chain reaction. A burst of antiprotons at maximum compression can allow target size to be significantly reduced. Antiprotons were previously shown to be a strong source of neutrons and pions; under conditions of high density, they enable a significant reduction in burn time and, hence, target size. Possible applications are discussed, including space propulsion and intense neutron and X-ray sources.