A general method for the correlation of forced convection heat-transfer data is proposed, which consists in plotting, against the Reynolds number, a dimensionless group representing the experimentally measured data from which film heat-transfer coefficients would be calculated, namely, [ (t 1 − t 2) Δt m ] (S A) , or its equivalent, h cG , multiplied by the two-thirds power of the group, (cμ k) . Data are cited from the literature which show that the resulting plots of heat-transfer data for flow parallel to plane surfaces and for fully turbulent flow inside tubes, coincide (when the properties are taken at the “film” temperature) with the best data on fluid friction plotted in the customary manner, as the friction factor 1 2 δ = ΔPg ρu 2 S A = R ρu 2 , against the Reynolds number. For flow at right angles to tubes, however, the friction and heat-transfer factors differ, the friction factors being higher. The equations successfully employed for representing heat-transfer data in streamline flow inside tubes have been modified for plotting with the same coordinates as used for turbulent flow ; and a quantitative allowance is suggested for the effect of free convection at low velocities by including a function of the group, . There is seen to be no relation between heat transfer and friction in the viscous region. The method of correlation here proposed is shown to be particularly valuable in the transition region between streamline and turbulent flow in tubes, since heat-transfer factors may show “dips” analogous to those for friction. The controlling variables in this region are fully discussed in the light of the available data.