In this paper the problem of natural convection from an isothermal elliptic tube with its major axis horizontal and placed in a micropolar fluid is investigated. The study is based on the solution of full conservation equations of mass, linear momentum, angular momentum and energy without boundary layer assumptions. The study focuses on the effect of the fluid material parameters and Rayleigh number on both flow and thermal fields. Prandtl number and ellipse axis ratio are kept constant. Results are presented for the local and average Nusselt numbers along with some details of both flow and thermal fields. In comparison with Newtonian fluids the study has shown that micropolar fluids display a reduction in heat transfer rate. (C) 2003 Published by Elsevier Ltd.