  We compute analytically the probability distribution of large deviations in
the spin-glass free energy for the Sherrington-Kirkpatrick mean field model,
i.e. we compute the exponentially small probability of finding a system with
intensive free energy smaller than the most likely one. This result is obtained
by computing the average value of the partition function to the power $n$ as a
function of $n$. At zero temperature this absolute prediction displays a
remarkable quantitative agreement with the numerical data.
