Protein-protein interactions form large and complex networks. Their visualisation can aid biologists in gaining new insights about the processes in cells and is, therefore, very useful for building sophisticated research tools. Often standard force-directed graph drawing algorithms are used for the visualisation of these networks. However, currently available visual interfaces to biological databases only show general interactions and cannot cope well with more complex networks with different types of interactions. This paper presents a new approach to the visual analysis of protein-protein interaction networks. It uses a combination of circular and force-directed graph drawing algorithms to compute visual representations of protein networks depending on the type of the selected interaction. Smooth transitions between subsequent drawings enable users to explore different functional clusters in these networks without getting lost in the entire network. The visualisation system has been tested with data from the BRITE database.