A slot interleaved multiple access (SIMA) scheme for distributed-queue dual-bus (DQDB) metropolitan area networks is proposed. In this scheme, all the active nodes will access the slots in an interleaved fashion. This scheme is very efficient for solving the bandwidth domination problem and the priority domination problem, which cannot be solved readily by the DQDB medium access control (MAC) protocol with a bandwidth balancing mechanism. An enhanced SIMA (ESIMA) scheme is proposed to solve the bandwidth allocation problem, which cannot be solved by the DQDB MAC protocol. Simulation results show that SIMA and ESIMA perform much better than the DQDB MAC on throughput as well as the access delay.