An experimental study was performed to investigate the effects of surface configuration and liquid subcooling on the critical heat flux for pool boiling on downward facing curved heating surfaces. The experiments involved quenching of heated hemispherical vessels into a large pool of water under well-controlled laboratory conditions. Local boiling curves were deduced using an inverse heat conduction code from the transient wall temperatures recorded by thermocouples embedded in the vessel wall. A significant spatial variation of the critical heat flux was observed on the vessel outer surface under both saturated and subcooled boiling conditions. Based on the local CHF data, a correlating equation was derived showing the linear dependence of the critical heat flux on the degree of subcooling and the nonlinear variation of the critical heat flux with the angular position along the heating surface. The effect of subcooling on the critical heat flux was found to be entirely different from the subcooling effect on the nucleate boiling heat transfer.