Abstract: Context-awareness is increasingly becoming an important capability in devices for ubiquitous computing environments. These devices use on-board sensors and history of user interaction to collect data that are used to adapt their behavior to suit with the current environment. There is a need to support real-time software in ubiquitous computing environments, especially in reactive systems, such as distributed and mobile sensors, location-based information services, etc. In these cases, both behavior and the interaction among devices depend on constantly changing environmental conditions, in addition to explicit user control. This characteristic requires specific system services to support the development and the runtime operation of real-time context-aware software. This implies that the underlying services must themselves be context-sensitive. In this paper, Reconfigurable Context-Sensitive Middleware (RCSM) is presented to facilitate real-time context-aware software in ubiquitous computing environments.