The ground state rotational spectra of HDCO and D2CO have been measured fro
m 5 to 2000 GHz. These new measurements together with older ones have been
fitted to a standard A-reduced Watson-type Hamiltonian. The accuracy of the
rotational and centrifugal distortion constants has been significantly imp
roved. It has to be noted that it was necessary to include octic constants.
The experimental constants are compared to ab initio predictions, (C) 1999
Academic Press.