The evolution of computer and communications systems in the past decade brings new opportunities for increased efficiency and accuracy of observational studies. In ongoing, large scale research studies, the problem of bridging organizational and analytical methods of the past to modern methods of data structure and control can consume considerable effort. A model for information flow in an observational study is sketched, and the flow is found inherently complex. This complexity and corresponding managerial demands are compounded by database file proliferation and by evolution of system hardware and software. Interactive, network-based database mapping and documentation tools are described as currently implemented in an SAS-based system for the management and analysis of several large epidemiologic studies.