This is the reference manual for the LeLisp implementation of the Sophtalk system. Sophtalk is a set of tools that enable one to program the interaction between objects following an event model of communication. System objects, called stnodes emit messages when significant events occur such as the termination of a computation a request for a service from another object, error conditions, etc. Messages circulate asynchronously in a network of stnodes. An stnode's type determines which messages it will receive, upon reception an action corresponding to the message and stnode instance is triggered. Messages may also circulate between processes. The manual describes the three modules of Sophtalk : stnode, a multicast communication mechanism : stio an extension of the standard LeLisp asynchronous and synchronous i/o mechanisms : and stservice, which offers interprocess communication at the shell and LeLisp levels.