  Two years of microwave background observations with the Cosmic Background
Imager (CBI) have been combined to give a sensitive, high resolution angular
power spectrum over the range 400 < l < 3500. This power spectrum has been
referenced to a more accurate overall calibration derived from WMAP. The data
cover 90 deg^2 including three pointings targeted for deep observations. The
uncertainty on the l > 2000 power previously seen with the CBI is reduced.
Under the assumption that any signal in excess of the primary anisotropy is due
to a secondary Sunyaev-Zeldovich anisotropy in distant galaxy clusters we use
CBI, ACBAR, and BIMA data to place a constraint on the present-day rms mass
fluctuation sigma_8. We present the results of a cosmological parameter
analysis on the l < 2000 primary anisotropy data which show significant
improvements in the parameters as compared to WMAP alone, and we explore the
role of the small-scale cosmic microwave background data in breaking parameter
degeneracies.
