Modeling and simulation in systems biology seeks to understand the dynamic behavior of living cells. Biological knowledge is quickly increasing, and modeling and simulation are now faced with systems of complex control, with stochastic effects and increasing size. Formal modeling approaches are thus essential for proper model verification and system prediction. The Biocomputing team develops and studies languages for modeling and simulating bio-molecular systems as well as static analysis methods. Our approach is based on concurrent programming languages with stochastic semantics.