The more information and data are produced by the actual information society, the more important become mechanisms and systems which organize the data and include information where to find which data. The most popular peculiarities of such information systems are metadata information systems (MIS) and catalogue systems (CS). The main difference between these systems is the extent of the information spectrum covered. Whilst e.g. catalogues for department stores or phone books are typical representatives of CS covering a relatively clearly outlined information spectrum (address, phone number, article no., price etc.), other systems cover a quite larger spectrum. Examples of this are environmental MIS such as the UDK (German: Umweltdatenkatalog, engl.:environmental data catalogue, see Swoboda et al., 1999) on a national basis or GELOS (Global Environment Information Locator Service, see GELOS, 2000 and ETC/CDS, 1999) and EIONET (European Environment Information and Observation Network, see EIONET, 1999) on an European basis. This chapter describes general aspects of the topic, outlines typical strengths and problems of existing systems and gives some impressions about trends and current activities in the field of MIS for geospatial data.