AbstractWith the ability to perform dynamic experiments in the environmental scanning electron microscope (ESEM), the evaluation of microporous polymer membranes via a scanning electron microscope has advanced beyond morphological and elemental analysis. By adjusting sample temperature and environmental chamber pressure, the process of condensing water onto the porous membrane surface can be achieved. In doing so, assessments about the uniformity of wetting in hydrophilic membranes can be obtained based on how the liquid water spreads. Variations in the shape of condensed water droplets formed on non‐water wetting structures will reflect the degree of hydrophobicity. This technique has proven useful in the characterization of hydrophobic spots on chemically modified hydrophilic structures and the dynamic examination of irregular wetting patterns in naturally hydrophilic membranes. © 1993 Wiley‐Liss,