Solid State Synthesis, Structure and Transport Properties of Compositions in the CaRu1-xTixO3-δ System. -The title compounds (0 ≤ x ≤ 1) are prepared by solid state reactions of RuO2-x, TiO2, and CaCO3 (alumina crucibles, 800-1300°C, 10-130 h) and characterized by powder XRD and conductivity measurements. They crystallize with the GdFeO3-type structure in the space group Pnma. Apart from CaRuO3 with a combined p-/n-type conductivity all the compounds are n-type semiconductors. The materials show high catalytic activity for propene oxidation and no activity for NO2 reduction.