This study was conducted to experimentally characterize the flow field created by the interaction of a single-expansion ramp-nozzle (SERN) flow with a hypersonic external stream. Data were obtained from a generic nozzle/afterbody model in the 3.5 Foot Hypersonic Wind Tunnel at the NASA Ames Research Center, in a cooperative experimental program involving Ames and McDonnell Douglas Aerospace. The model design and test planning were performed in close cooperation with members of the Ames computational fluid dynamics (CFD) team for the National Aerospace Plane (NASP) program. This paper presents experimental results consisting of oil-flow and shadow graph flow-visualization photographs, afterbody surface-pressure distributions, rake boundary-layer measurements, Preston-tube skin-friction measurements, and flow field surveys with five-hole and thermocouple probes. The probe data consist of impact pressure, flow direction, and total temperature profiles in the interaction flow field. Spaid, Frank W. and Keener, Earl R. and Hui, Frank C. L. Ames Research Center AFTERBODIES; FLOW DISTRIBUTION; FLOW VISUALIZATION; GAS STREAMS; HYPERSONIC FLOW; NOZZLE FLOW; WIND TUNNEL TESTS; COMPUTATIONAL FLUID DYNAMICS; EXHAUST GASES; NATIONAL AEROSPACE PLANE PROGRAM; PRESSURE DISTRIBUTION; SHADOWGRAPH PHOTOGRAPHY; SKIN FRICTION; TEMPERATURE PROFILES...