A small single-channel fuel cell prototype was built with the objective of monitoring the appearance and transport of water droplets in the gas channels in usual operating conditions. It allows the simultaneous observation of droplets and of their local effects on current density. The first results show that the air flow rate seems to control the transition between two different water removal mechanisms: a plug flow when the air stoichionnetry is low, with significant disturbances in the local current density, pressure drop and fuel cell performance, and a more conventional flow with steadier removal of smaller droplets when the stoichionnetry is higher. (C) 2009 Elsevier B.V. All rights reserved.