Two systems, chromium and chromium oxide films on Pt(111), as well as rutile TiO$\sb2$(110) surfaces, have been investigated using Low Energy Ion Scattering Spectroscopy (ISS), X-ray Photoelectron Spectroscopy (XPS), Low Energy Electron Diffraction (LEED), and Scanning Tunneling Microscopy (STM). The films of metal Cr and chromium oxide were grown by Cr vapor deposition in UHV and under an oxygen pressure of 2 x 10$\sp{-6}$ mbar, respectively. Both films grow in a step-flow mode. The Cr film is pseudomorphic to the Pt(111) substrate within the first two monolayers (ML). At higher coverages, the chromium overlayer adopts a bcc (110) surface structure and forms three-dimensional elongated islands oriented along the three close-packed directions of the Pt(111) surface. A self-organized Cr/Pt surface alloy is formed upon annealing 1.5-3 ML Cr/Pt(111) to 800 K. This alloy exhibits a highly-symmetric hexagonal network of one-atom-wide dislocation lines, with a unit cell dimension of 17.3 A. STM images reveal a strong variation of the local electronic structure due to the presence of a regular array of two-dimensional Cr clusters containing 10 atoms. For the chromium oxide, a well ordered p(2 x 2) structure is observed within the first 2 ML and attributed to the epitaxial growth of metastable Cr$\sb3$O$\sb4.$ At higher coverages, a ($\surd$3 x $\surd$3)R30$\sp\circ$ structure appears, due to formation of the stable Cr$\sb2$O$\sb3$ phase. The influence of surface preparation procedures on the structure and appearance of TiO$\sb2$(110) has been investigated. After initial cleaning and with increasing annealing temperature, the segregation of Ca impurity to the surfaces of fresh TiO$\sb2$(110) single crystals has been observed. As revealed by LEED and STM, a $\left\lbrack {6\enspace0\atop 3\enspace 1}\right\rbrack$ structure is formed as an overlayer, with row-like features along the (001) direction. In line with the Ca 2p$\sb{3/2}$ peak position of 347.4 eV, we propose formation of a CaTiO$\sb3$-like compound, oriented with its (110) face parallel to the substrate. Upon annealing a sputtered rutile TiO$\sb2$(110) surface and cooling it down in an oxygen background pressure, STM images show a highly-ordered (4 x 2) structure. We believe a new phase, anatase (110), is formed on the rutile TiO$\sb2$(110) surface