Rape et al. have recently demonstrated that the order in which APC/C targeted proteins are degraded is determined by the processivity of multiubiquitination of these substrates. Processive substrates acquire a polyubiquitin chain upon binding to the APC/C once and are degraded. Distributive substrates bind, dissociate and reassociate with the APC/C multiple times before acquiring an ubiquitin chain of sufficient length to insure degradation. In addition, distributive substrates that dissociate from the APC/C with short ubiquitin chains are targeted for deubiquitination (Rape et al., 2006). Paradoxically, although the multiubiquitination of cyclin A is distributive and later substrates of APC-Cdc20 such as Securin are processive (Rape et al., 2006), Cyclin A is degraded prior to Securin and Cyclin B. The mechanisms insuring this order have not yet be determined.