The essential objective in atmospheric pollen research is to learn how much of what kinds of allergenic pollen are likely to be inhaled by sensitized persons at any time and in any locality. This objective may be amplified in further detail as follows: (1) to assist in the clinical evaluation, locally and generally, of known allergenic pollens, (2) to discover, identify, and help to evaluate new allergenic pollens, (3) to clarify the role of meteorologic, topographic, and other local factors affecting pollen prevalence and pollen dispersal, and (4) to find areas where, as a result of natural advantages or control measures, or both, the air is relatively or entirely free from pollens of particular species. Obviously, air analysis furnishes an excellent yardstick by which to judge the anti-allergenic value of weed eradication campaigns and to test the truth of advertised claims for pollen-free vacation resorts. At present all routine sampling