  We study the anisotropy of the cosmic microwave background (CMB) in cold and
mixed dark matter (CDM and MDM) models, with non scale-invariant primordial
power spectra (i.e. $n \neq 1$) and a late, sudden reionization of the
intergalactic medium at redshift $z_{rh}$. We test these models against recent
detections of CMB anisotropy at large and intermediate angular scales. We find
that current CMB anisotropy measurements cannot discriminate between CDM and
MDM models. Our likelihood analysis indicates that models with blue power
spectra ($n \simeq 1.2$) and a reionization at $z_{rh} \sim 20$ are most
consistent with the anisotropy data considered here. Without reionization our
analysis gives $1.0 \le n \le 1.26$ (95 % C.L.) for $\Omega_b = 0.05$.
