In the present study, experiments were carried out to determine the influence of fluid flow and liquid subcooling on flow boiling heat transfer across horizontal tubes. Extensive data were taken using Freon-113. The data cover wide ranges of velocity (1.5 to 6.9 m/s) and liquid subcooling (29 to 100 °C) at pressure ranging from 122 to 509 kPa. Cylindrical electric resistance heaters made of Hastelloy-C with diameter of 6.35 mm were used. The azimuthal wall temperature distributions were measured with five thermocouples around the heaters. The data were compared with Chen's two-mechanism model with modification for subcooled flow boiling. A new nucleate boiling suppression factor for cross flow was developed. The improved model could predict the present data and Yilmaz and Westwater's (1980) data well with a mean error ratio of 1.02 and standard deviation of 0.17.