This document is the final report for a research project aimed at producing a prototype system for on-line translation of typed dialogues between speakers of different natural languages. The work was carried out jointly by SICS and SRI Cambridge. The resulting prototype system (called Billingual Conversation Interpreter, or BCI) translates between english and Swedish in both directions.The Major components of the BCI are two copies of the SRI Core Language Engine, equipped with English and Swedish grammars respectively. These are linked by the transfer and disambiguation components. Translation takes place by analyzing the source-language sentence into Quasi Logical Form ( QLF), a linguistically motivated logical representation, transferring this into a target-language QLF, and generating a target-language sentence. When ambiguities occur that cannot be resolved automatically, they are clarified by Querying the appropriate user. The clarification dialogue presupposes no knowledge of either linguistics or the other language. The prototype system has a broad grammatical coverage, a initial vocabulary of about 1000 words together with vocabulary expansion tools, and a set of English-Swedish transfer rules. The formalism developed for coding this linguistic information make it relatively easy to extend the system. We believe that the project was successful in demonstrating the feasibility of using these techniques for interactive translation applications, and provides a sound basis for development of a large scale message translator system with potential for commercial exploitation.The main sections of this report are the following: * A non-technical introduction, summarizing the BCI's design , and containing a sample session. * An overview of the Swedish version of the CLE. * A detailed discussion of the theory and practice of QLF transfer. * A description of the interactive disambiguation method. * Suggestions for possible follow-on projects aimed in the direction of practically usable commercial systems.