The intent was the generation of information relative to the basic definition, identification, and assessment of the national odor problem. Three factors - odor producing potential of industrial odorant sources, atmospheric vulnerability, and size of population - were developed separately and then combined for an indication of the odor problem potential of each three digit postal zip code area in the nation. Local air pollution control agencies were surveyed to identify areas where they believe that significant odor problems exist. Within the principal cities of each of seven representative metropolitan areas, two-day technical field investigations and public opinion surveys were conducted. Sensory evaluations of odor were also performed in Philadelphia, Pennsylvania. Odor problem potential exists in most metropolitan areas in the United States. But, primarily because of meteorological factors, the probability of encountering odor problems is greatest in the Appalachian and California Coastal metropolitan areas. A large number of residents - perhaps as many as 25 million - perceive odors as problems and desire some form of abatement. The results of the mail survey and personal interviews of local air pollution control agencies indicated that when concentrations of air pollutants can be related to amounts of property damage and/or ill health, abatement criteria (e.g., minimum levels of emissions) can be established and enforced. However, in cases of air pollutants causing only odors, such relationships are generally non-existent. Consequently, odor abatement criteria, if any, are typically based on number of complaints and inadequately backed by nuisance laws. (Author)