  I review recent progress towards a detailed understanding of the power
spectrum of cosmic string perturbations induced on the Microwave Background
(CMB). The use of a simple analytic model allows to include important effects
that have not been included in previous studies. These effects are potential
fluctuations on the last scattering surface (the Sachs-Wolfe effect) and
Doppler CMB perturbations. These previously neglected fluctuations are shown to
dominate over post-recombination fluctuations (Gott-Kaiser-Stebbins effect) on
angular scales less than about $2^\circ$ assuming that no reionization occurs.
The effective power spectrum index $n_{eff}$ is calculated on COBE scales and
is shown to be somewhat larger than 1 ($1.35 \lsim n_{eff} \lsim 1.5$). After
normalizing the model on COBE data and string simulations, I derive the
predicted values of $({{\delta T}\over T})_{rms}$ for several ongoing CMB
experiments on medium and small angular scales. A comparison is also made with
current observations and predictions of models based on inflation.
