An investigation was conducted on the residual oil saturation (ROS) measurement techniques developed during the last fifteen years. Knowledge of precise ROS measurements is required for EOR project planning. The advantages, limitations, and problems of each one of the techniques are presented in tabulated form. Also, some of the possible improvements in the measurement techniques for the residual oil saturation are summarized. The following residual oil saturation techniques are discussed: core analyses, well logging, backflow tracer tests, material balance and well testing, newly developed gravity log methods, and interwell residual oil saturation measurements. Several aspects left to be improved in both instrumentations and data interpretation on pressure coring, back-flow tracer tests, well logging, material balance calculations, well testing, and interwell ROS measurements are presented. A nuclear magnetism log-inject-log method is proposed in which the need for porosity measurement for determining residual oil saturation is eliminated. 91 refs., 3 tabs.