The well-known net present value (NPV) rule advocates accepting all investment projects that have a positive NPV. The NPV rule makes economic sense since positive-NPV projects are expected to create economic value. But what should a manager do if the total investment capital needed to fund the available positive-NPV projects exceeds the budgeted capital available? This note illustrates and discusses the profitability index, one tool that is used to assist managers in such constrained situations.