A novel laminar annular film condensation model that can be applied to microchannels of arbitrary cross-sectional shapes has been developed. The modelincorporates the effects of gravity, surface tension, interfacial shear, and vapor pressure gradient, and is used to study the effect of channel shape and wallcurvature on condensation. The model is applied to microchannels with circular, square, horizontal and vertical elliptical, horizontal and verticalrectangular, triangular and inverted triangular cross sections. Comparisons are made for R134a condensing at Tsat = 50°C, and at a mass flux of 500kg m-2s-1, and wall subcooling of 6°C. Local variations of wall curvature affect condensate distribution, which leads to heat transfer enhancement incertain geometrical shapes. It is shown that triangular channels yield the best heat transfer performance. The model can be used to assess condensation in avariety of irregular shaped channels that can now be fabricated using emerging manufacturing techniques.