Multimedia backbone local area networks (LAN) have recently become key components of private networks as fiber distributed data interface (FDDI) backbone LANs. This paper discusses the architecture of loop-type high-speed multimedia backbone LANs (MBLANs) based on B-ISDN technology as the next generation LAN targeting the introduction stage of the B-ISDN age and its realization. This paper highlights problems to be solved with respect to the adoption of B-ISDN technologies, such as synchronous digital hierarchy (SDH) and assyncrhonous transfer mode (ATM) technology, to MBLANs and proposes some solutions. It also presents high-speed MBLANs with transmission rate of 622 Mbit/s and the basic hardware implementations of the system.