  We compare the latest cosmic microwave background data with theoretical
predictions including correlated adiabatic and CDM isocurvature perturbations
with a simple power-law dependence. We find that there is a degeneracy between
the amplitude of correlated isocurvature perturbations and the spectral tilt. A
negative (red) tilt is found to be compatible with a larger isocurvature
contribution. Estimates of the baryon and CDM densities are found to be almost
independent of the isocurvature amplitude. The main result is that current
microwave background data do not exclude a dominant contribution from CDM
isocurvature fluctuations on large scales.
