An efficient symbolic elimination algorithm for the stochastic process algebra tool CASPA. CASPA is a stochastic process algebra tool for performance and dependability modelling, analysis and verification. It is based entirely on the symbolic data structure MTBDD (multi-terminal binary decision diagram) which enables the tool to handle models with very large state space. This paper focuses on an extension of CASPA’s modelling language by weighted immediate actions. We discuss the pertaining semantics and present an efficient symbolic algorithm for the elimination of vanishing states. A non-trivial case study illustrates the usage features of CASPA, from graphical model specification to numerical analysis.