This week we describe how standard NPV analysis might lead to incorrect decisions when we fail to account for the impact of (or upon) firm flexibility. We then describe the three most common types of real options that firms face in practice and then explain how decision trees might be used to arrive at an approximation of the value of the real option that is embedded within a project. We conclude by considering empirical evidence on the take-up of real options analysis and discuss the situations in which real options analysis might most be needed.