  We report the detection of a massive rotating disk around the high-mass Class
0 candidate NGC 7538S. The disk is well-resolved with BIMA (HPBW =3.7") in 3.4
mm continuum and in H13CN J = 1 - 0. It is seen nearly edge on and has a size
of ~ 30,000 AU. A young, powerful outflow perpendicular to the rotating disk is
mapped in SiO J = 2 - 1 and HCO+ J = 1 - 0. The dynamical age of the outflow is
< 10,000 yr. The velocity gradient seen in H13CN is consistent with Keplerian
rotation. Assuming that the gas is gravitationally bound, the mass of the
central object is ~ 40 Msun. The mass of the continuum ``disk'' is <= 100 Msun
and has a luminosity of 10^4 Lsun. H13CN gives a mass ~ 400 Msun for the
rotating disk, and ~ 1000 Msun for the extended (20") envelope. Our
observations confirm that this is an extremely massive protostar in its
earliest stages.
