Rule-based systems in which confiict resolution occurs require a control strategy. Many systems use domain-independent, fixed control strategies. This paper shows that effective conflict resolution often requires domain-specific knowledge. Moreover, defining control knowledge may be as difficult as defining domain knowledge. We present the ORBS model and implementation of a rule-based systems environ­ment which supports complex and dynamic control strategies, and the interactive development or these strategies. ORBS and earlier systems are compared with respect to language, control, and environmental support for development or control. Four examples of control using ORBS are discussed: emulating a con­ventional system, separating domain knowledge from scheduling knowledge, using an agenda-based strategy, and dynamically changing a strategy during execution. The ORBS environment provides machine-aided construction or scheduling strategies through a catalog of scheduling functions from which strategies can be constructed, a skeleton scheduler, a scheduling editor, a scheduling tracer, and a break package. Finally, the paper discusses a model for system implementation of control from user-provided examples.