Process algebras model the dynamic behaviour of systems, and have recently been used to model biological systems. This talk will introduce this modelling formalism and illustrate its use through examples. Bio-PEPA is a biological process algebra developed in the PEPA group in Informatics at the University of Edinburgh. It explicitly includes spatial aspects of models, allowing for different compartments to be defined. A key advantage of Bio-PEPA is that once a model is defined, multiple forms of analysis are possible using the Bio-PEPA Eclipse Plug-in software. This analysis includes deterministic behaviour through ordinary differential equations, and stochastic simulation. Additionally, the software can export to other analysis tools. A model of protein trafficking in the cell and other examples will be discussed.