  Observations at mid-infrared (4.8-17.65 um) and radio (0.7-1.3 cm)
wavelengths are used to constrain the structure of the high-mass star-forming
region W3 IRS5 on 0.1'' (200 AU) scales. Two bright mid-infrared sources are
detected, as well as diffuse emission. The bright sources have associated
compact radio emission and probably are young high-mass stars.
  The measured sizes and estimated temperatures indicate that these sources
together can supply the observed far-infrared luminosity. However, an optically
thick radio source with a possible mid-infrared counterpart may also contribute
significant luminosity; if so, it must be extremely deeply embedded.
  The infrared colour temperatures of 350-390 K and low radio brightness
suggest gravitational confinement of the H II regions and ongoing accretion at
a rate of a few 10^-8 M0/yr or more. Variations in the accretion rate would
explain the observed radio variability. The low estimated foreground extinction
suggests the existence of a cavity around the central stars, perhaps blown by
stellar winds.
  At least three radio sources without mid-infrared counterparts appear to show
proper motions of ~100 km/s, and may be deeply embedded young runaway OB stars,
but more likely are clumps in the ambient material which are shock-ionized by
the OB star winds.
