The distribution of OB stars and dust in a milky way field at(l,b,)= 335,0)*

New photoelectric UBV photometry for 103 stars and MK spectroscopy for 110 stars are presented in a 21 deg² field at (l, b) = (335°, 0°); these are mostly OB stars and brighter than V = 14.4. Combined with other observations from the literature, these provide photoelectric UBV and slit or objective prism spectra for 111 of the 112 SLS stars in this region, and photoelectric measurements for a further 84 non-OB stars, some with spectra. Most of the stars may be separated into three groups associated with the spiral structure of the inner galaxy, A = Ara OB1 at 1.34±0.05 kpc (51 members), B at 2.41±0.08 kpc (25 members), and C at 3.69±0.23 kpc (19 members).The dust is distributed in two distinct clouds, one in the local arm at 190±30 pc and the other in an interarm cloud of variable extinction at 690±70 pc. The dust may have the same two-colour reddening properties as found in Cygnus.