High time resolution ISEE-1 and -2 observations of upstream field-aligned ion beams at several crossings of the Earth's bow shock indicate that some beams are due to high-energy magnetosheath particles leaking through the shock into the upstream region. The distribution immediately downstream of these oblique (&thgr;Bn~50¿) shocks consists of a 'core' of directly transmitted, slightly heated ions plus a crescent-shaped, high-velocity distribution, centered roughly on a magnetic field in the direction toward the upstream region, with a fairly well-defined low velocity cut-off.