Nilpotent Blocks of Quasisimple Groups for the Prime Two

We examine nilpotency amongst blocks of positive defect of the quasisimple groups for the prime 2. We show that every nilpotent block of a quasisimple group has abelian defect groups, and prove a conjecture of Puig concerning the recognition of nilpotent blocks in the case of quasisimple groups. Explicit characterisations of nilpotent blocks are given for the classical, alternating and sporadic simple groups.