This study was conducted to evaluate the deflection of partially prestressed concrete beams (PPC) under static and cyclic fatigue loading covering the boundaries of fully prestressed and fully reinforced. Two analytical models were developed, one model for predicting deflection under service monotonic loading and the other for predicting deflection under cyclic fatigue loading. Both models were derived based on interaction between the tensile steel and concrete through bond and slip of reinforcement between the cracked sections. The developed models were compared With extensive experimental results and showed to reproduce, within a good degree of accuracy, load-deflection response of PPC beams tested under both static and cyclic fatigue loading-Several conclusions were drawn on the basis of analytical results, verified by experimental evidence. In designing prestressed concrete beams for fatigue loading, careful consideration should be given to the increase in reinforcement stresses induced by cyclic creep of concrete. This phenomenon is particularly important in cracked fully prestressed beams where the stresses were observed to increase significantly with number of cycles. This phenomenon does not only reduce the fatigue life of the beams but also results in a significant increase in their deflections under cyclic loading. The reinforcing steel in the partially prestressed beams plays a major role in reducing the phenomenon of steel stress increase under cyclic loading which results in enhancing their fatigue life and deformation performance! cracking, deflection,). It was found also, that parameters, such as bond strength, crack spacings and bar diameters have little influence on the service load-deflection response post cracking indicating that the contribution of the uncracked regions of the concrete member to its overall flexural rigidity can be practically neglected.