Scanning tunneling microscopy (STM) of (001) GaAs samples immersed in aqueous solutions has been used to assess the effectiveness of a standard bromine‐methanol chemomechanical polish to produce flat surfaces over length scales from 5 to 1000 nm. The STM images reveal irregular 100‐nm features coexisting with large areas of average roughness of the order of a few nanometers. The precision, stability, and reproducibility of these images suggest that immersion STM could be used to study surface chemical processes in real time.