The paper reports the results of an experimental study in which heat transfer and pressure drop data were taken during condensation of R-113 inside five horizontal tubes. One tube was smooth, and four were internally finned. The smooth tube data were taken as a basis for comparison with the data of the internally finned tubes. Over the mass flux range tested, an enhancement in the heat transfer coefficients was obtained as high as 51% over the smooth tube results on a nominal area basis. Correlation equations are proposed for predicting the overall heat transfer coefficient and pressure drop during condensation inside internally finned tubes.