  Nearly all astrophysical and cosmological data point convincingly to a large
component of cold dark matter in the Universe. The axion particle, first
theorized as a solution to the strong charge-parity problem of quantum
chromodynamics, has been established as a prominent CDM candidate. Cosmic
observation and particle physics experiments have bracketed the unknown mass of
the axion between approximately a $\mu$eV and a meV. The Axion Dark Matter
eXperiement (ADMX) has successfully completed searches between 1.9 and 3.7
$\mu$eV down to the KSVZ photon-coupling limit. ADMX and the Axion Dark Matter
eXperiement High-Frequency (ADMX-HF) will search for axions at weaker coupling
and/or higher frequencies within the next few years. Status of the experiments,
current research and development, and projected mass-coupling exclusion limits
are presented.
