  We consider pure isocurvature cold dark matter models in the case of open and
closed universe. We allow for a large spectral tilt and scan the 6-dimensional
parameter space for the best fit to the COBE, Boomerang, and Maxima-1 data.
Taking into account constraints from large-scale structure and big bang
nucleosynthesis, we find a best fit with $\chi^2 = 121$, which is to be
compared to $\chi^2 = 44$ of a flat adiabatic reference model. Hence the
current data strongly disfavour pure isocurvature perturbations.
