This paper examines fully developed laminar flow and conjugated forced convection heat transfer in curved rectangular channels. The wall average Nusselt number, <(Nu)over bar>, is presented as a function of the wall conduction parameter, phi, the Dean number, De, and the channel aspect ratio, lambda. Secondary flow streamlines for the case of lambda=1/2 are presented to illustrate the enhanced stability in curved rectangular channels in comparison with curved square channels. A curve illustrating the relationship between phi(eff), defined as the value of phi at which a constant wall temperature boundary condition can be assumed, and De is presented for several values of lambda. The solution for straight channels is also included, and it is found that phi(eff) is independent of lambda for lambda less than or equal to 1/4.