We present scanning tunneling microscopy data illustrating the evolution of the decapped GaAs(001) surface following annealing in stages from 450 to 540 degrees C. After annealing at 450 degrees C a (2x4) reconstruction is formed by kinked rows of two As dimer unit cells. Following annealing in the 475-500 degrees C range small isolated regions of (4x2) reconstruction are visible, with a considerable increase in disorder of the remaining (2x4) reconstructed areas. Annealing at higher temperatures causes the (4x2) structure to become increasingly dominant. We have noted significant differences in the surface morphology as a function of annealing time. Our images of the (4x2) surface are similar to those recently reported by other groups but we propose a new structural model.