Scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED) have been used to examine the structure of ordered adlayers of Ca on TiO2(110)-1 × 1 formed by metal vapor deposition. A comparison is made with structures formed by segregation of Ca from the bulk, with similar structures being found for the two preparation methods below a monolayer coverage. At low coverages, rows of width ∼0.6-0.9 nm develop in the  and  azimuths. At coverages equivalent to a single calcium layer, a c(6×2) overlayer is formed. At coverages above a single layer, a disordered structure develops and a LEED pattern with (2 -0.1 1 0) symmetry is observed.