Growth of Candida albicans biofilms and production of extracellular matrix were monitored by dry weight, colorimetric and radioisotope assays, and by scanning electron microscopy. Under static incubation conditions synthesis of matrix material was minimal, but increased dramatically when developing biofilms were subjected to a liquid flow with the result that the cells were enveloped in extracellular polymer. These findings suggest that production of matrix material could contribute to the resistance of biofilm cells to antifungal agents in vivo.