  Extensive recent work on the Sunyaev-Zeldovich (S-Z) effect reflects major
progress in observational capabilities of interferometric arrays, the improved
quality of multi-frequency measurements with upcoming ground-based and
stratospheric bolometer arrays, and the intense theoretical and experimental
work on the small scale structure of the cosmic microwave background (CMB)
radiation. I briefly describe the effect and discuss its significance as a
major cosmological probe. Recent results for the gas mass fraction in clusters
and the Hubble constant (largely from measurements with the BIMA and OVRO
interferometric arrays) are discussed. Also reviewed are results from the first
determination of the CMB temperature at the redshifts of two clusters (from
measurements with the MITO and SuZIE experiments), and recent work on the CMB
anisotropy due to the S-Z effect.
