  I describe the recently proposed quantization of bosonic string about the
mean-field ground state, paying special attention to the differences from the
usual quantization about the classical vacuum which turns out to be unstable
for d>2. In particular, the string susceptibility index $\gamma_{\rm str}$ is 1
in the usual perturbation theory, but equals 1/2 in the mean-field
approximation that applies for 2<d<26. I show that the total central charge
equals zero in the mean-field approximation and argue that fluctuations about
the mean field do not spoil conformal invariance.
