[en] The three ground-state transitions of CH have been observed in the direction of selected H II regions and dark clouds and the profiles compared with those of 4829 MHz H₂CO and OH (both ground state at 1667 MHz and excited state at 6035 MHz). The 3264-MHz F = O - 1 transition was in emission in all cases; the 3335-MHz F = 1 - 1 showed absorption in the direction of seven bright H II regions; towards four of these there was also absorption at the 3349-MHz F = 1 - O frequency over part of the profile. All sources with 3349-MHz absorption showed absorption by excited OH. It is suggested that, if CH is excited predominantly by collisions with H₂ molecules in the presence of far-IR radiation, higher densities are required to produce absorption at 3349 than at 3335 MHz. The strongest CH emission towards Sgr A occurs near zero velocity; at 3264 MHz it consists of three components, one of which is probably associated with the radio continuum north of the Galactic Nucleus. (author)