A self-assembled monolayer of dodecanethiol is grown onto (111) oriented gold by vacuum phase depositionand studied by ultrahigh vacuum scanning tunneling microscopy (STM). The films consist of domains thatexhibit the c(4 × 2) overstructure of the hexagonal (√3 × √3)R30 of alkanethiols on gold. The domain sizeis only limited by the terrace size of the underlying gold. By higher resolution scans a new phase of thec(4 × 2) structure consisting of four inequivalent molecules that display different heights in the STMimages is discovered.