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Measuring the environmental condition of waterways is of interest to river managers, governments and the community. In the State of Victoria, Australia and elsewhere, there is concern that environmental values of streams are declining and that information about the environment, needs to be considered when river management decisions are being made. / This thesis explores the use of environmental indicators as a tool to assist management of rivers. The promise of indicators is that they can turn large amounts of environmental data into simple, timely results and thereby provide an effective means of incorporating this information into river management decisions. It is also suggested that indicators will be useful for measuring the outcomes of management intervention and provide feedback on the effectiveness of strategies. / Can environmental indicators live up to this promise? This thesis examines this question by reviewing indicator systems that have been developed by others and then exploring, in detail, the Index of Stream Conditions (ISC) that is is intended as a tool to assist the management of rivers in Victoria. I argue that environmental indicators have a role at the level of regional waterway management authorities but only if they are closely aligned with managers’ needs. Without consideration of non-technical issues, indicators are unlikely to be used, so it is important to establish a balance between pragmatic constraints and the need for scientific rigour. A procedure to achieve this balance is described in this thesis and was applied to the development of the ISC. Selection of indicators and the choice of indicator frameworks are explored and the value judgements behind the interpretation of indicator scores are examined. / It is also important to consider the accuracy and sensitivity of indicators. Possible objectives for the use of indicators include benchmarking, detecting change and providing information to trigger management intervention. Case studies are used to explore the performance of indicators in practical applications in streams in Victoria in relation to these objectives. Extensive use is made of non-traditional statistical procedures, including bootstrapping, and results are presented that show the likely variance of indicator scores and the relationship between indicator objectives and required sampling effort.