The paper presents data on map collections in governmental, academic, public, institutional, and corporate libraries in Ohio. Only those collections containing over 100 maps are included in the study. The overall objective is to increase awareness of cartography as a source of information. A more specific objective is to provide comparative, descriptive, and statistical information related to and on the availability of cartographic materials in the state of Ohio. The study is based on the third edition of the directory "Map Collections in the United States and Canada," (1978)--a project of the Geography and Map Division of the Special Libraries Association. Twenty-seven map collections were selected from the directory for inclusion in this study. Whereas in the directory, entries were arranged alphabetically by city and by name of library, data in this analysis are organized according to institutional characteristics. The general characteristics are identification, staff, collections, organization of materials, and usage and cooperative aspects. Topic headings related to these general characteristics include type of library, date of establishment of collection or department, number and type of personnel employed, size of collection in terms of total number and annual growth, major geographic areas and subject specialization, special cartographic collections, chronological coverage of collections, organization of materials for use, system of classification in use, depository status, audience served, hours of service, seating capacity, number of readers, and interlibrary loan and reproduction facilities. Data are presented in tabular form. Explanations of symbols and figures are offered to aid the reader in interpreting the data. (Author/DB)