Measurements of critical heat flux (CHF) were performed for a horizontal annular channel (diameters 11.2 and 54 mm, approx. 1 m heated length) in which the eccentricity of the inner heater was varied. Measurements for low mass fluxes (up to 1600 kg/m2/s) using freon-12 at a pressure of approx. 10.3 bar and saturation inlet conditions show a strong influence of eccentricity on CHF. The influence of the mass flux on CHF is only moderate. The data trend is discussed on a basis of the flow pattern under which the phenomenon occurs. A model based on the analysis of an intermittent flow pattern was developed. The model explains satisfactorily the trend of the experimental data.