This is a book on combinatorial group theory.This is a book about certain ways of representing sporadic simple groups and about graphs associated with these representations. The book gives a classification of all permutation representations of low rank of the sporadic groups, together with the parameter values for all associated vertex-transitive graphs. Sufficient information is given about most of the groups and graphs to enable readers to re-construct and study these representations themselves. Elementary techniques for analysis of finite vertex-transitive graphs are carefully explained, making the book not only an essential reference for experts in Group Theory and Graph Theory, but also an excellent starting point for graduate students and researchers wishing to work in this area.This is a book about certain ways of representing sporadic simple groups and about graphs associated with these representations. The book gives a classification of all permutation representations of low rank of the sporadic groups, together with the parameter values for all associated vertex-transitive graphs. Sufficient information is given about most of the groups and graphs to enable readers to re-construct and study these representations themselves. Elementary techniques for analysis of finite vertex-transitive graphs are carefully explained, making the book not only an essential reference for experts in Group Theory and Graph Theory, but also an excellent starting point for graduate students and researchers wishing to work in this area.This book addresses certain ways of representing sporadic simple groups and the graphs associated with these representations. It provides descriptions of all permutation representations of rank up to five of the sporadic groups and gives an introduction to practical computational techniques required for studying finite vertex-transitive graphs. The authors offer sufficient information about most of the groups to enable readers to reconstruct and slS&