SLACnet is a Local Area Network (LAN) using Ethernet* and the Xerox Network System (XNS) protocols. It currently provides datagram, virtual circuit, remote procedure call and file transfer services. SLACnet connects together multiple DECt VAX computers running VMS and an IBM* 3081K mainframe running VM/SP. The IBM 3081 is connected to the Ethernet via a Device Attachment Control Unit (DACU). Th e source code consists of about 25K lines of C and 8K lines of assembler. About 16K lines are common to the IBM VM/SP and the DEC VMS implementations. SLACnet has been in production 24 hours a day since April, 1985, and coexists with DECnet on the same Ethernet. SLACnet is designed to keep the impact on the IBM 3081 to a minimum, and provide easy to use conversion between VM/SP and VMS sequential files. SLACnet provides bulk transport of up to a Gbyte/day of physics data between the VAXes and the IBM 3081, as well% the transfer of program source files, listings, object code, etc. This talk describes how SLACnet fits into VM, the services provided, the mapping between the DEC and IBM worlds, the performance of the various layers, the impact on VM/SP, and the development effort involved. Show Partial Abstract