Intrinsic defects of the nearly stoichiometric (110) surface of TiO2 have been studied by means of scanning tunneling microscopy. Temperature treatment at 870 less than or equal to T less than or equal to 1070 K in ultrahigh vacuum induces changes of the orientation of single steps. Line defects along [001] and oxygen vacancies are formed simultaneously as predominant surface defects under these conditions. Atomically resolved scanning tunneling microscopy images make it possible to determine their geometric structures. Simple structural models are derived to explain the high stability of electrostatically neutral [001] single steps and [001] line defects at TiO2(110).