Abstract: This paper presents and discusses the LOTOS specification of a real-time parallel kernel. The purpose of this specification exercise has been to evaluate LOTOS with respect to its capabilities to model real-time features with a realistic industrial product. LOTOS was used to produce the formal specification of TRANS-RTXC, which is a real-time parallel kernel developed by Intelligent Systems International. This paper shows that although timing constraints cannot be explicitly represented in LOTOS, the language is suitable for the specification of co-ordination of real-time tasks, which is the main functionality of the real-time kernel. This paper also discusses the validation process of the kernel specification and the role of tools in this validation process. We believe that our experience (use of structuring techniques, use of validation methods and tools, etc) is valuable for designers who want to apply formal models in their design or analysis tasks.