Surface x-ray diffraction has been employed, in situ, to measure InAs(001)-(2x4) surface phases under technologically relevant growth conditions. For the As-rich (2x4) phase, the authors obtain good agreement between the data and the beta 2(2x4) surface reconstruction model. Comparison of our measurements on the (2x4) phase measured close to the metal-rich phase transition to models from density functional theory suggests a mixture of alpha 2(2x4) and beta 2(2x4) surface structures present on the surface. (C) 2008 American Vacuum Society.