The general purpose of this investigation was to study the separated flow field associated with a fin-body juncture. Specific objectives included: (a) determining the severity and extent of aerodynamic heating, (b) providing flow visualization results to illustrate the flow structure, and (c) obtaining a data base of heat-transfer and surface-pressure measurements upon which to develop future analytical relations to predict peak interference heating levels. Tests were conducted at Mach 5 over a unit Reynolds number range of 4.5 to 26 million per foot. A fin-cone model was used. The data consist of surface- pressure distributions, heat-transfer measurements using the phase-change paint technique, and schlieren and oil-flow photographs. Results are presented for several fin-cone geometries to include fin sweep and fin-cone gap. Where possible, comparisons are made with fin-flat-plate data.