Fluid flow and heat transfer characteristics in a serpentine channel with a series of right angle turns were studied numerically for two dimensional steady laminar flow with constant properties. Constant heat flux was applied to the upper and the lower walls. Computations were performed in the periodically fully developed region. Effects of each parameter (Reynolds number, Prandtl number and two geometrical factors) on the friction factor, the local and the overall heat transfer were investigated and the results were compared with the ones from the fully developed straight channel. The heat transfer enhancement was explained in conjunction with the complex flow mechanisms such as flow impingement, merge of recirculations etc. Significant heat transfer enhancement was obtained in high Prandtl number fluid flow. In typical serpentine channels, unjustifiably high pressure drop was not required to achieve small factor of heat transfer improvement. 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 of Re = 100 - 500.