We have developed a high-bandwidth, photon-counting, x-ray detector for x-ray imaging experiments. It consists of an x-ray photocathode, an optional microchannel plate (MCP), optional electrostatic optics, and a subnanosecond phosphor. The detector can be used for two-dimensional imaging with a subnanosecond framing camera or one-dimensional imaging with a Reticon or streak-camera readout. Several versions of the one-dimensional detector have been developed. The MCP version employs a photocathode on the front surface of the MCP, and the transmission-photocathode version consists of a photocathode deposited on a thin polypropylene foil. The output electrons from the MCP or the transmission photocathode are accelerated into a fast phosphor deposited on a coherent fiber-optic faceplate. Both detectors can be enhanced with the use of electrostatic electron optics to compress the output electrons in one dimension. The best parameters achieved to date are a time resolution of 400 ps, spatial resolution of 100 ,um, and electron compression of 10:1. Quantum efficiencies of 40% have been achieved. Effective quantum efficiencies greater than 100% have been achieved with the one-dimensional electrostatic optics. Data are presented on the efficiency, time response, and spatial resolution of the one-dimensional detectors.