The multi-agent systems (MAS) paradigm is one of the most important and promising approaches to occur in computer science during the 90s. However, for an effective use of the agent technology in real life applications, specific programming languages are required. CLAIM is a high-level agent-oriented programming language that combines cognitive aspects such as knowledge, goals and capabilities and computational elements such as communication, mobility and concurrence in order to reduce the gap between the design and the implementation phase. CLAIM has an operational semantics that is a first step towards the verification of the built MAS. The language is supported by a distributed platform called SyMPA, implemented in Java, compliant with the specifications of the MASIF standard from the OMG, that offers all the necessary mechanisms for a secure execution of a distributed MAS. CLAIM and SyMPA have been used for developing several applications that proved the expressiveness of the language and the robustness of the platform.