Bacterial growth on crystalline naphthalene was measured and found to be related tot he dissolution rate of the substrate. No evidence for enhancement of substrate availability due to bacterial influence could be detected. Using a model based on dissolution kinetics for substrate availability and Monod kinetics for bacterial growth it was possible to simulate bacterial growth on naphthalene. This model is widely applicable for growth of micro-organisms on poorly water-soluble substrates and can easily be adapted to a more complex system such as microbial growth on substrates adsorbed to matrices.