  To better understand the physical properties of accretion disks in high-mass
star formation, we present a study of a 12 high-mass accretion disk candidates
observed at high spatial resolution with the Australia Telescope Compact Array
(ATCA) in the NH3 (4,4) and (5,5) lines. Almost all sources were detected in
NH3, directly associated with CH3OH Class II maser emission. From the remaining
eleven sources, six show clear signatures of rotation and/or infall motions.
These signatures vary from velocity gradients perpendicular to the outflows, to
infall signatures in absorption against ultracompact HII regions, to more
spherical infall signatures in emission. Although our spatial resolution is
~1000AU, we do not find clear Keplerian signatures in any of the sources.
Furthermore, we also do not find flattened structures. In contrast to this, in
several of the sources with rotational signatures, the spatial structure is
approximately spherical with sizes exceeding 10^4 AU, showing considerable
clumpy sub-structure at even smaller scales. This implies that on average
typical Keplerian accretion disks -- if they exist as expected -- should be
confined to regions usually smaller than 1000AU. It is likely that these disks
are fed by the larger-scale rotating envelope structure we observe here.
Furthermore, we do detect 1.25cm continuum emission in most fields of view.
