HI in early-type galaxies

We summarise the HI properties of early-type galaxies, in particular the di fferences in HI morphologies observed in early-type galaxies of different l uminosities. We find that in low-luminosity early-type galaxies the HI is a lmost always in a disk-like structure, with central surface densities high enough for star formation to occur. In a few luminous early-type galaxies t he HI is also in a disk or in a ring-like structure, but in most luminous e arly-type galaxies the HI has a relatively irregular morphology. The surfac e densities in the Hr disks in luminous early-type galaxies are lower than in the Hr disks in low-luminosity early-type galaxies and no large-scale st ar formation should occur in these disks. We discuss these different HI cha racteristics in the context of other properties of early-type galaxies that correlate with luminosity.