The water quality monitoring activities required of the States under the Federal Water Pollution Control Act Amendments (PL92-500) will require resources well beyond what is likely to be available, if current systems structures and operating procedures are followed. This paper describes some quantitative procedures developed to optimize monitoring resource allocation, with the goal of getting the greatest possible return on a limited monitoring budget. The ambient and effluent standards which form the basis of the monitoring system are described. Stochastic inputs to the river basin which lead to violations of these standards are identified, and progress in characterizing these variations mathematically is discussed. Quantitative priority-setting procedures for the two principal monitoring activities (ambient and effluent), which take into account these stochastic inputs, are reviewed. Both procedures are designed to tell the state agency planner where the next increment of resource should be expended to maximize alternative monitoring objective functions. Approaches to integrating these two primary monitoring functions and opportunities for further applications of operations research techniques to improve program effectiveness and efficiency are suggested.