A numerical investigation has been conducted to study the effects of free convection on forced convection heat transfer in the thermal entrance region between vertical parallel plates with upward flow of low Prandtl-number fluids. Numerical solutions are given for two thermal conditions of parallel plates: one wall heated with the other wall insulated; and both walls heated in the same uniform states. The results are discussed in conjunction with those of uniform irrotatinal velocity. Numerically predicted friction factors and local Nusselt numbers are compared with their counterparts for pure forced convection. For use in practical applications, correlation equations are developed for the friction factors and the local Nusselt numbers.