The “Fault-Tolerant Insulin Pump Therapy” is based on the Continuous Subcutaneous Insulin Injection technique which combines devices (a sensor and a pump) and software in order to make glucose sensing and insulin delivery automatic. These devices are not physically connected together and they come with the necessary features to detect malfunctions which they may have. As the patient’s health is the most important, the therapy has to be able to work despite the fact that hardware and/or software faults have or may ocurr. This paper presents the development cycle for the Insulin Pump Therapy Control System case study, starting from requirements and reaching the implementation following a top-down approach. It will show how the Coordinated Atomic Actions (CAAs) structuring mechanism can be used for modelling Faul-Tolerant (FT) systems and how CAA-DRIP development environment is used to implement it.