The Ocean Engineering Department at Woods Hole Oceanographic Institution will undertake an instrumentation and technology development project to design and construct an unmanned, untethered vehicle for performing and servicing long-term deep ocean benthic experiments. This vehicle has been named ABE for the Autonomous Benthic Explorer. Design criteria call for it to be launched from any oceanographic research ship and be able to remain on site for several months. During this time span it must periodically move about in its acoustic navigation net, taking pictures and making a variety of scientific measurements. At the end of its mission, it is to be recovered on command. ABE will complement and extend the capabilities of manned submersibles, particularly DSV ALVIN, as well as remotely operated, tethered systems such as ARGO/JASON. These systems will still be required for initial surveys and installations. However, ABE shall have the ability to remain at a deep sea research site for long periods or to return to a previously surveyed site to observe changes. The instrumentation development project is in anticipation of planned research initiatives requiring long-term observations of seafloor features such as hydrothermal vents and mid-ocean ridges.