Indicators have been variously categorized. A favourite classification, devised to describe types of sustainability indicator, distinguishes pressure, state and response indicators. What exactly is the role of indicators and how useful are they, particularly in the field of land use and environmental planning? What are their advantages and disadvantages? What are the potential traps into which the designer of indicators may fall? And can the indicators that are in use be improved upon, or should we instead be seeking better alternatives? The difficulty is that statements of policy objectives, the very bedrock upon which the design of performance indicators is founded, are in practice not often in a form that makes indicator design and extraction easy or, indeed, possible. Unless indicators are well matched to the objectives of the policies they are being used to track or evaluate, any decisions that stem from the information and analysis the indicators generate are likely to be distorted.