Spectral Characterizations of Some Distance-Regular Graphs

When can one see from the spectrum of a graph whether it is distance-regular or not?We give some new results for when this is the case.As a consequence we find (among others) that the following distance-regular graphs are uniquely determined by their spectrum: The collinearity graphs of the generalized octagons of order (2; 1), (3; 1) and (4; 1), the Biggs-Smith graph, the M22 graph, and the coset graphs of the doubly truncated binary Golay code and the extended ternary Golay code.