Office Automation by electronic text processing has not reduced the amount of paper used for communication and storage. The present boom of FAX-Systems proves this tendency. With this growing degree of office automation the paper-computer interface becomes increasingly important. To be useful, this interface must be able to handle documents containing text as well as graphics, and convert them into an electronic representation that not only captures content (like in current OCR readers), but also the layout and logic structure. We describe a system for the analysis of business letters which is able to extract the key elements of a letter like its sender, the date, etc. The letter can thus for instance be stored in electronic archival systems, edited by structure editors, or forwarded via electronic mail services. This system was implemented on a Symbolics Lisp machine for the high level part of the analysis and on a VAX for the low and medium level processing stages. Some practical results are presented and discussed. Apart from this application our system is a useful testbed to implement and test sophisticated control structures and model representations for image understanding.