Abstrect : In°A Frobenius theorem for blocks", Inventiones Math ., 56, M . Broué and the author introduce the so called nilpotent blocks and determine its structure, namely the generalized decomposition numbers . Here we recall some of these results and announce the following one : the direct factor of the grupp álgebra associated with a nilpotent block is isomorphic to the (n x n)-matrix álgebra over the defect grupp álgebra, for a suitable n .