This study is based on the premise that urban functions should be located in response to inner and inter activity relationships. Being one of the important and growing urban functions, office activity was examined to study activity relationships and locational processes. Its growth, changing location in the urban context, and its national pattern was studied in a historical perspective. Then its future growth and development were reviewed. The office types incorporated in this research are: Manufacturing, Transportation, Communication, Utilities, Government, Services, Insurance and Real Estate. These types cover about 900 of the office employment in the New York region. Using a vertical hierarchy office types were broken down into three levels: Headquarter office, Middle office, and Local office. The criterion to differentiate them was the physical jurisdiction of each office level. A one-way matrix was constructed as a tool to trace the "in" and "between" interactions of office functions. Factors that bring about the location of office activity in downtown or suburban office parks were researched from previous studies. Matrices were used for developing a relationship between office types and their locational needs. Concrete application confirms its (matrix) usefulness though the scaler value judgements used are somewhat subjective, based on the knowledge of and research done by the author. The matrices when completed give a clear picture of the relationships, within an activity and between activities / and their location needs, which can be a valuable aid in locating office activity specifically and urban functions in general.