Fluid flow and heat transfer characteristics in a serpentine channel with a series of right-angle turns are studied numerically for two-dimensional steady laminar flow with constant properties. Constant heat flux is applied to the upper and lower walls. Computations are performed in the periodically fully developed region. The effects of each parameter (Reynolds number, Prandtl number, and two geometrical factors) on the friction factor and the local and overall heat transfer are investigated. The results are compared with those from fully developed flow in straight channels. The heat transfer enhancement is explained in conjunction with complex flow mechanisms, such as flow impingement and merging of recirculation zones. Significant heat transfer enhancement is obtained in high Prandtl number fluids. In typical serpentine channels, unjustifiably high pressure drop is not required to achieve small factors of improvement in heat transfer. In typical serpentine channels, while the distance between two inside corners is equal to the channel height, the channel whose pitch is 1.5 times as large as the channel height gives the highest heat transfer enhancement in the range Re = 100-500.