We report a study of molecular-scale, uniform mixed self-assembled monolayers (SAMs) of alkanethiols with different terminal groups on atomically flat Au(111) surfaces prepared using the kinetically trapped method reported by us previously for methyl-terminated alkanethiol SAMs. The terminal groups studied include carboxylic acid, amine, hydroxyl, and methyl. Mixed SAMs are characterized by low-current scanning tunneling microscopy (STM). Molecular-resolution STM images show that these mixed SAMs formed at higher solution temperatures are uniform for different terminal groups, compositions, and chain lengths, similar to methyl-terminated SAMs reported previously.