A numerical study of laminar natural convective heat transfer in air from a pair of equi-temperature horizontal cylinders placed one above the other in a vertical plane was carried out. Prime attention was focused on how heat transfer characteristics of the upper cylinder are affected by center-to-center separation distance between two cylinders (CCD). The study was limited to Rayleigh number ranging from 2 x 10(4) to 2 x 10(5) . The vertical center-to-center separation distance between the cylinders was varied from two to ten cylinder diameters. A finite difference scheme based on the integration of the governing equations over finite cells was used. Temperature profiles around two cylinders, and heat transfer coefficients for each cylinder were obtained. The effect of center-to-center separation distance between the cylinders on heat transfer from the upper cylinder was considered. For assessing the accuracy of the current computational approach the results are compared with the experimental results reported by Sparrow and Niethammer .