  We combine detections of anisotropy in the Cosmic Microwave Background
radiation with observations of inhomogeneity in the large-scale distribution of
galaxies to test the predictions of models of cosmological structure formation.
This combination probes spatial scales varying by three orders of magnitude,
including a significant region where the two types of data overlap. We examine
Cold Dark Matter models with adiabatic density perturbations, isocurvature
models, and a topological defects model. We set upper limits on the neutrino
mass and find the primordial power spectrum needed to reconcile an apparent
disagreement between structure formation observations and direct observations
of cosmological parameters.
  Present and future observations of Cosmic Microwave Background anisotropy
suffer from foreground contamination. We develop detailed predictions for
microwave emission from radio and infrared-bright galaxies and the
Sunyaev-Zeldovich effect from clusters. We present realistic simulations of the
microwave sky, produced as part of the `WOMBAT Challenge' exercise, and
introduce a pixel-space method for subtracting foreground contamination which
can be tested on these simulations.
