The HI/OH/Recombination line survey of the Milky Way. The THOR project is a northern Galactic plane survey (15 %3C l %3C 67deg and |b| %3C +-1deg) in HI, four OH, and 19 H alpha recombination lines as well as in the L-band continuum from 1 to 2GHz. The spatial resolution of the Very Large Array (VLA) in the C-array of about 20'' is essential for comparison with other Galactic plane surveys.