The present study numerically investigates two-dimensional laminar fluid flow and heat transfer past a circular cylinder in an aligned magnetic field using the spectral method to insure the accuracy of results. For the purpose of controlling vortex shedding and heat transfer, numerical simulations to calculate the fluid flow and beat transfer past a circular cylinder are performed for different Reynolds numbers of 100 and 200 and for different Prandtl numbers of 0.02 (liquid metal), 0.7 (air) and 7 (water) in the range of 0 less than or equal to N less than or equal to 10, where N is the Stuart number (interaction parameter) which is the ratio of electromagnetic force to inertia force. The present study reports the detailed information of flow and thermal quantities on the cylinder surface at different Stuart numbers. As the intensity of applied magnetic fields increases, the vortex shedding formed in the wake becomes weaker and the oscillating amplitude of lift coefficient decreases. The flow and thermal fields become the steady state if the Stuart number is greater than the critical value, which depends on the Reynolds number. Thus the drag and lift coefficients and Nusselt number representing the fluid flow and heat transfer characteristics also vary as a function of Stuart number. (C) 2004 Elsevier Ltd. All rights reserved.