Summary of Conclusions and Recommendations: The levels of mercury contamination found in freshwater fish in Sweden and Finland are similar to those found in such fish in the United States. On the other hand, fish consumption in this country is regarded as generally somewhat less than in the region of Scandinavia. Medical examinations of heavy eaters of contaminated fish have not revealed conclusive evidence of mercury-related disease in either Sweden or Finland. Nevertheless, the body burdens of mercury of some of those having the heaviest intake of fish in both of those countries were as high as the lower levels reported in persons with methylmercury poisoning in Japan. The major conclusion derived from these and other findings was that it seems unlikely that we will find overt mercury poisoning from the consumption of fish or other food products, as normally marketed, in this country. This is not to say that there may not be a few individuals, who because of high consumption of contaminated fish may have signs of mercury poisoning or suffer possible subclinical effects, including delayed neurologic or intellectual damage. Also, possibly infants or children may have impaired development. As yet, no systematic studies have been undertaken, even in the known areas of human exposure in Sweden and Japan, to identify such subclinical effects. Although we appear to be on safe ground, it is urgent (1) to determine whether subtle health effects are present and (2) to use all possible means to reduce exposure to mercury immediately.