Continuing interest by OSHA-NIOSH and by EPA regarding the adequacy of current sulfur oxides standards has prompted a reappraisal of the available human and animal data. Results of animal studies were not considered to be useful in establishing the original air quality standards in 1970, even though there was good reason to consider them as a prime source of information. Considering the multitude of species tested, using every conceivable method of administration and range of doses, a fairly consistent pattern of effect has emerged. Further, the majority of the human clinical data and even the industrial data parallel and support the results found in the animal studies. However, neither the animal studies, the clinical investigations nor the industrial experiences agree with the recently reported community epidemiological studies that are currently receiving attention. It may well be that the toxicological data are correct in that there are no important long-term effects from exposure to the sulfur oxides. Certainly the laboratory studies, animal or human, do not support more stringent standards for either the occupational or the community environment.