Internal mixtures of inorganic and organic material are common in tropospheric aerosols, with organic matter typically comprising 10 to 90% of fine aerosol mass. One special class of organic material commonly found in atmospheric aerosols is surface-active species, including fatty acids, proteins, and humic-like substances. It has been suggested that surface-active organic molecules partition to the gas-aerosol interface of aqueous atmospheric aerosols in an “inverted micelle” configuration, thus forming an organic film around the aqueous core. Recent laboratory studies suggest that, if organic films are a common feature of aqueous aerosols, this could significantly affect atmospheric composition and climate. However, despite their potential significance, the existence of surface films on aqueous aerosols has not yet been confirmed unambiguously under a wide range of conditions. We will present the results of pendant drop tensiometry and ellipsometry studies designed to identify the range of aerosol compositions for which the inverted micelle morphology may exist. We will focus on classes of surface active organic compounds which are expected to have distinct phase behavior at atmospherically relevant pH, such as short and long-chain fatty acids, diacids, proteinaceous material, and secondary organic aerosol material, as well as mixtures containing multiple organic species. The effects of surface films on aerosol heterogeneous chemistry will also be discussed.