ADAMO is a data management system for defining data and manipulating them from FORTRAN programs. A form of the Entity-Relationship (ER) model and the data flow diagrams of structured analysis have been combined to provide a system suited to algorithmic work. The FORTRAN interface consists of calls to a subroutine package with a few data manipulation primitives. Data items are visible in variables carrying meaningful names; the code is compact and readable. The ER data structures, mapped onto tables, are compatible with a relational data base management system. Tools have been written to copy tables to and from a relational data base. The system has been used for several applications in the fields of event simulation and reconstruction, online systems, detector description, support tools and packages.