The monolayer behavior of two series of sheet-shaped tetrakis(phenylethynyl)benzene derivatives has been investigated by means of surface pressure-area isotherms, Brewster angle microscopy, and surface potential-area isotherms. The tetraynes 1 and 2 are characterized by two terminal hydroxy substituents fixed either to the ortho or to the para positions of the central aromatic nucleus via flexible alkyl spacers. All compounds form monolayers at the air/water interface with an edge-on arrangement of the enlarged flat molecular parts. A spontaneous aggregation of the edge-on oriented rigid aromatic cores takes place resulting in two-dimensional island structures immediately after spreading. Further monolayer characteristics of the sheet-shaped tetrayne amphiphiles 1 and 2 during compression are dictated by their different molecular symmetries.