In this work we present Bio-PEPA, a process algebra for the modelling and the analysis of biochemical networks. It is a modification of PEPA, originally defined for the performanceanalysis of computer systems, in order to handle some features of biological models, suchas stoichiometry and the use of general kinetic laws. Bio-PEPA may be seen as an intermediate, formal, compositional representation of biological systems, on which different kindsof analysis can be carried out. Bio-PEPA is enriched with some notions of equivalence.Specifically, the isomorphism and strong bisimulation for PEPA have been considered andextended to our language. Finally, we show the translation of a biological model into thenew language and we report some analysis results.