A template-free method for the production of polypyrrole nanofibres is presented. By adding a small amount of bipyrrole into the oxidative polymerization of pyrrole, a drastic change in the morphology of the observed material is observed form large, granular particles to nanofibrils with an average diameter of 20 nm. This simple procedure allows for the production of polypyrrole nanofibers without the presence of surfactants or other structural directing agents. The polypyrrole nanofibers can form stable water dispersions which can be cast into films of sufficient quality to function as chemical sensors for analytes such as ammonia.