The microwave spectrum of acetaldehyde is critically reviewed and augmented through calculations which include the effects of internal rotation and centrifugal distortion. Since the primary objective of this review is to provide microwave spectral transitions applicable to radio astronomy studies, the review encompasses only the ground state rotational spectrum of the most abundant isotopic form of acetaldehyde, 12CH312CH16O. While all measured transitions are included, the predicted transition frequencies were limited to J?12 in the range of 900 MHz to 250 GHz. In addition to this spectral information, the review includes the rotational constants, centrifugal distortion constants, inertial rotation parameters, electric dipole moment, structural data, moments of inertia, and constants relating to the barrier to internal rotation.