Heat transfer, flooding point and film thickness during reflux condensation of refrigerant R134a in an inclined small diameter tube (ID: 7 mm, length: 500 mm) are experimentally investigated. Also a physical model for laminar reflux condensation of a pure saturated vapour in an inclined small diameter tube is presented. The theoretical results for the film thickness and the heat transfer are compared with the experimental data. It is found that the inclination angle has a significant effect on the heat transfer coefficient and the flooding point. The calculated values for the film thickness and the mean heat transfer coefficient are in good agreement with the experimental data. The deviation is less than 15%. (C) 2004 Elsevier Ltd. All rights reserved.