Solar energy exploitation for assisting the operation of reverse osmosis (RO) seawater desalination plants was investigated. A hybrid solar-assisted steam cycle was designed in order to provide the required shaft work to drive the RO plant high pressure pump. Two problems have been analyzed. The design problem concerned the determination of the optimum plant characteristics with respect to membrane modules and solar system size for different capacity levels and various sites. Operational aspects of already installed solar assisted desalination plants with respect to plant capacity and regional climatological particularities were also studied. The methodology adopted was based on an appropriate mathematical formulation of the climatological effects on the solar-assisted desalination plant efficiency. The optimization problems studied were solved using mathematical programming techniques. Generalized design curves were produced for process, structural, and operational variables, while the effect of secondary plant parameters was also studied.