Experiments, performed both in water and air, yielded natural convection heat transfer coefficients for cubes positioned in as many as 13 orientations in the gravity field. The orientation-related variations in the heat transfer were in the 10-12% range for water and in the 2-5% range for air. When represented in terms of the Nusselt and Rayleigh numbers, the water and air data differed by about 10%. The data were used to assess the prediction methods of King and of Lienhard. The former overpredicted the data by 40-58%, while the latter, although more accurate, underpredicted the data by as much as 23%. To correlate the data for the cube, the sphere, and the short vertical cylinder (height = diameter), all bodies of unity aspect ratio, a new characteristic length was formulated. The new length is based on the surface area of the body and on the square root of the area of the projection of the body on a horizontal plane. With the newly defined Nusselt and Rayleigh numbers and with an already established Prandtl number factor, the data were very tightly correlated. Flow visualization performed in water indicated that the flow was laminar and that there was no separation of the flow at the corners of the cube.