Data are presented for natural and forced convection heat transfer from the outside of a single 3/4-in-dia tube to saturated water in the pressure range from 535 to 1550 psia. Nonboiling and nucleate boiling at low heat flux are considered for vertical and horizontal tubes. Water chemistry control is shown to be important in obtaining reproducible data. A new factor, suspended solid material in the boiling medium, is found to influence the nucleate boiling data in a manner similar to that of a dissolved gas.