In this short review, the calculation of the next-to-next-to-leading order
QCD corrections to the inclusive radiative decay B -> X_s gamma is described. I
summarize the salient features of the calculational framework adopted, discuss
the results obtained in the last few years, and indicate the technical tools
that made the NNLO calculations possible. I conclude by comparing the current
NNLO theoretical estimate for the branching ratio with the experimental
measurement and by briefly discussing the size and origin of the residual
theoretical uncertainty.Comment: 18 pages, 7 figures. Invited review for Modern Physics Letters