The 6 x 6 and root39 x root39 phases on Ag/Ge(I 1 1) have been studied by scanning tunneling microscopy (STM). Four types of 6 x 6 configurations are found which all consist of a root3 x root3 layer with six extra Ag adatoms per 6 x 6 unit cell. These reconstructions show either mirrored or complementary relations. We observe interesting transitions between the different 6 x 6 reconstructions. The root39 x root39 surface appears to have five extra Ag atoms per unit cell. By using various tip biases, we show that the root39 x root39 domain orientation can be changed. Surface structure models of the root39 x root39 and 6 x 6 phases are proposed based on the HCT structure of the underlying root3 x root3 surface. (C) 2003 Elsevier Science B.V. All rights reserved.