This paper presents the design of a parabolic-trough solar-collector system for water desalination in Gaza, Collector-aperture and rim-angle optimization together with the receiverdiameter selection are presented. A comparison of concentrating collectors against conventional flat-plate collectors is presented. It is shown that for large scale water production the parabolictrough collectors are more efficient than the flat plate ones. The analysis considers visible radiation transfer, IR radiation exchange, conductive and convective losses and energy transferred to a fluid flowing through the collector tube. The collector may have a tilted northsouth axis, an east-west axis or it may fully track the sun and geometric parameters associated with tracking the sun are considered.