The series of the SrTi1-xCOxO3-delta polycrystalline samples has been prepared via solid-state reaction in air. The structural study shows that a solid solution exists for all compositions, such as 0 less than or equal to x less than or equal to 0.9, which discards the presence of ferromagnetic and metallic cobalt clusters for the low level of cobalt substitution. The existence of systematic extra peaks on the electron diffraction patterns for x > 0.5 indicates that the oxygen vacancy ordering is responsible for the superstructures (2a(p) x 2a(p) x 4a(p), where the subscript "p" refers to the perovskite subcell). The oxygen nonstoichiometry is confirmed by thermogravimetric analysis. The magnetic properties reveal a maximum in the magnetic moment per mole of cobalt for x approximate to 0.10, However, the clear lack of strong ferromagnetism does not suggest that a diluted magnetic semiconductor (DMS)-type behavior is induced in SrTiO3 as Co is substituted for Ti. The transport properties along the SrTi1-xCOxO3-delta line are explained by considering the substitution of a Co3+/Co4+ mixed valency, which decreases the room-temperature resistivity by at least 5 orders of magnitude as one goes from SrTi0.9Co0.1O3-delta to SrTi0.1CO0.9O3-delta.