The transmission probability of an ultracold cascade three-level atom throu
gh micromaser systems is calculated and analyzed. It is shown that the micr
omaser systems can be used as velocity selectors for ultracold three-level
atoms. The velocity selectivity is better for ultracold three-level atoms t
han for ultracold two-level atoms, and is better in a two-cavity system tha
n in a one-cavity system. [S1050-2947(99)03210-2].