Atomic force microscopy (AFM) has been used to investigate the surface of ultrafiltration and microfiltration ceramic membranes. The AFM has been shown to resolve the feature of the gamma-Al2O3 selective skin layer of ultrafiltration membranes providing information on both the size and shape of the gamma-Al2O3 particles as well as the surface roughness of the skin. When applied to study alpha-Al2O3 microfiltration membranes the AFM has been shown to yield results very similar to those obtained by conventional scanning electron microscopy.