These proceedings collect the papers selected for the 2nd International Conf- ence on Interoperating GeographicInformationSystems held in Zur .. ich, Switz- land, 10-12 March, 1999. Interoperabilityhasbecomeanissueinmanyareasofinformationtechnology in the last decade. Computers are used everywhere, and there is an increasing need to share various types of resources such as data and services. This is es- ciallytrueinthecontextofspatialinformation.Spatialdatahavebeencollected, digitized and stored in many di?erent and di?ering repositories. Computer so- ware has been developed to manage, analyse and visualize spatial information. Producing such data and software has become an important business oppor- nity. In everydayspatialinformation handling in manyorganisationsand o?ces, however, interoperability is far from being a matter of fact. Incompatibilities in data formats, software products, spatial conceptions, quality standards, and models of the world continue to create as synchronicity among constituent parts of operating spatial systems. As a follow-upto the ?rst InternationalConference on Interoperating Geographic Information Systems held 1997 in Santa Barbara, California, the Interop'99 tries to provide a scienti? c platform for researchers in this area. Theinternationalprogramcommitteecarefullyselected22papersforpres- tation at the conference and publication in this volume. Additionally, this v- ume contains three invited contributions by Gio Wiederhold, Adrian Cuthbert and Gun .. ther Landgraf. Every paper was sent to three members of the program committee and other experts for review. The reviews resulted in a three-day single-track conference program that left some room for a few half-day tutorials on various topics regarding GIS interoperability.