When a decision maker considers possible returns business project or investment, he often faces the problem that  these returns are not all received at the same time, and thus he  must make some adjustments to take account of his time  preference for money. After a review of discounting, a utility  theory approach is made by developing a two-attribute utility function u(x, t) which represents the desirability of an income of x at a time t in the future. Assumptions to simplify the assessment  of this function are considered. Then u(x, t) is used to form a  criterion for evaluating infinite time streams of income.