Hydrogen starvation results in an inhomogeneous distribution of gases within fuel cells and stacks. An inhomogeneous reactant distribution significantly changes the current density distribution over the active cell area and can cause high cathode potentials due to the presence of oxygen in the anode electrode domain. High cathode potentials result in corrosion of the carbon support and thus lead to irreversible cell degradation. A PEMFC single cell assembly was utilised for detailed investigations of these phenomena. The cell was operated with low stoichiometries and in dead-end mode. Product gas analyses were utilised for determining the degradation phenomena.