We present scanning tunneling microscope (STM), low-energy electron diffraction, Auger electron spectroscopy, and scanning electron microscope results on the growth of Ag on Si(001)(2X1). At room temperature Ag is adsorbed only at the silicon S(B) steps at first and preferentially forms dimers during further growth. At higher Ag coverages an inhomogeneous layer which does not cover the surface completely is formed and Ag islands grow with Ag(111)Si(001). At a substrate temperature of 770 K Ag forms a homogeneous layer which covers the surface completely. This layer shows a novel (2X3) reconstruction, which shows a strong bias polarity dependence in the STM images. On the top of this (2X3) layer, three-dimensional Ag islands grow with Ag(001)Si(001).