The rapid increase in environmental measurements during the past few decades is associated with (1) increasing awareness of the complex relations linking biological responses to atmospheric variables, (2) development of improved data acquisition and handling equipment, (3) the application of modeling to environmental problems, and (4) the implementation of large, cooperative studies of international scope. The consequences of man's possible alteration of the environment have increased our interest in the complex nature of biological responses to meteorological variables. This has generated activity in both measurements and in the application of modeling techniques. The virtual explosion of modeling activity is also associated with the development oflarge computers. The testing of these models has demonstrated the need for more, different, and better environmental data. In addition, technological developments, such as integrated circuits, have reduced the cost, power consumption, and complexity of data acquisition systems, thus promoting more environmental measurements. The emergence of scientific cooperation on a global scale has increased measurement activities markedly. The International Geophysical Year (1958) has been followed by the International Hydrologic Decade, the International Biological Program, the Global Atmospheric Research Program, and a host of environmental studies of a regional nature that have all emphasized field data collection.