Information on oil and water production, volume of water injected, core analyses, and well completion data was collected on 28 red fork sand water-flood projects for comparison and evaluation of results. An average water injection efficiency of 35 percent, an average water-injected to oil-produced ratio of 16.8:1, and an average loss outside the flood pattern of approximately 45 percent of the injected fluid resulted in an oil recovery to January 1, 1969, of only 5.6 percent of the pore volume, or 9.1 percent of the initial stock-tank oil in place. The principal causes of poor oil recovery from these projects are the losses of large quantities of injection water from the flood patterns through oriented, natural fracture systems or zones of high permeability and excessive channeling of injection fluids from input wells to oil wells. For more efficient operation and a higher percentage of oil recovery from the red fork sand and other low-permeability-sand waterflood projects, directional orientation of both induced- and natural-fracture systems should be determined during early development. The success of a low-permeability-sand waterflood project depends to a large extent upon the orientation of the injection wells with the fracture system. Work done in cooperation with the state of Oklahoma.