The effect of a horizontal partial porous partition on heat transfer and flow structure in a differentially heated square cavity is investigated. While the fluid flow is assumed to be governed by Navier-Stokes equations, fluid saturated porous media is assumed to be governed by Darcy's equations. Standard Galerkin method of finite element formulation is applied for discretization of the system of equations. The non-linearities in the discretized equations are treated with Newton-Raphson scheme. The code developed is tested for validation for modified Rayleigh number Ra* up to 400. The code is then applied to a differentially heated square cavity with a horizontal partial porous partition. While the thickness of the porous partition is found to have appreciable effect on heat transfer and flow field, width of the porous partition is found to have insignificant bearing on heat transfer except when the partition is very small and compatible to the thickness of the boundary layer developed. During the experimentation Darcy number and Rayleigh number are assumed to be constant at 10−4 and 106 respectively. © 1994, MCB UP Limited