This book contains a thorough study of symmetric algebras, covering topics such as block theory, representation theory and Cli?ord theory. It can also serve as an introduction to the Hecke algebras of complex re?ection groups. Its aim is the study of the blocks and the determination of the families of characters of the cyclotomic Hecke algebras associated to complex re?ection groups. Iwouldliketothankmythesisadvisor, MichelBrou e, forhisadvice.These Springer Lecture Notes were, after all, his idea. I am grateful to Jean Michel for his help with the implementation and presentation of the...