Emission and absorption characteristics of a V-groove cavity are analyzed and the predicted results are compared with experimental measurements. The configuration considered consists of a flat black base with diffusely emitting, specularly reflecting side surfaces. The local directional emissivity is given as a function of emission angle, position, side wall emissivity, and cavity geometry. The results show that, with proper selection of the parameters, the cavity can be made a strong emitter and absorber for directions which are nearly normal to the cavity opening area, and a weak emitter and absorber for directions which correspond to large angles measured from the normal. A simple expression for cavity depth is suggested for closely approaching the optimum condition of maximum directionality of the cavity. Some predicted heat transfer rates for surfaces composed of many cavities are also presented. These results illustrate the potential value of employing specially prepared grooved surfaces in applications where control of radiant energy exchange is required.