In this paper, an experimental study on the heat transfer characteristics of two-phase flow boiling of some alternative refrigerants to HCFC-22, on air/refrigerant horizontal enhanced surface tubing, is presented. Correlations have been proposed to predict the heat transfer characteristics such as average heat transfer coefficients, as well as pressure drops of alternatives to R-22; such as R-507, R-404A, R-407C, R-410A and R-408A in two-phase flow boiling inside enhanced surface tubing. In addition, it was found that the refrigerant mixture＇s pressure drop is a weak function of the mixture＇s composition. It was found that the correlations were applicable to the entire heat and mass flux, investigated in the present study, for the proposed blends under question. The deviation between the experimental and predicted values for the heat transfer coefficient and pressure drop were less than +/- 20, and +/- 35 per cent, respectively, for the majority of data.