The Special Study Committee on Well Spacing and Allocation of Production of the American Petroleum Institute has, in connection with studies of the influence of well spacing on oil recovery, accumulated comprehensive data on the reservoir characteristics and oil recovery of approximately 100 oil reservoirs scattered throughout the United States. These data have been made available to the authors for critical analysis to determine from actual field data what relationship might exist between ultimate oil recovery and well spacing. In the course of this analysis it has been found that the recovery from these field is dependent on oil viscosity, reservoir pressure decline, and formation permeability. No evidence was found that their recovery is influenced by their well spacing.