This paper discusses the integration of highly distributed loads into power system control actions, focusing on achieving full responsiveness and nondisruptiveness. It reviews existing initiatives and challenges in load control, emphasizing the need for direct load control over price response to enable fast, predictable control opportunities, particularly for ancillary services like regulation and contingency reserves. The paper explores centralized, hierarchical, and distributed control architectures, their benefits, and drawbacks, especially in relation to legacy power system control architecture. It also considers the implications for supporting communications infrastructure, such as advanced metering infrastructure (AMI). Fully responsive load control is illustrated through examples of thermostatically controlled loads and plug-in electric vehicles (PEVs). The paper concludes by discussing the dual objectives of load control, the choice of input signals, and the potential of distributed control strategies.This paper discusses the integration of highly distributed loads into power system control actions, focusing on achieving full responsiveness and nondisruptiveness. It reviews existing initiatives and challenges in load control, emphasizing the need for direct load control over price response to enable fast, predictable control opportunities, particularly for ancillary services like regulation and contingency reserves. The paper explores centralized, hierarchical, and distributed control architectures, their benefits, and drawbacks, especially in relation to legacy power system control architecture. It also considers the implications for supporting communications infrastructure, such as advanced metering infrastructure (AMI). Fully responsive load control is illustrated through examples of thermostatically controlled loads and plug-in electric vehicles (PEVs). The paper concludes by discussing the dual objectives of load control, the choice of input signals, and the potential of distributed control strategies.