Persistent organic pollutants (POPs) are fat-soluble chemicals like dioxins, polychlorinated biphenyls (PCBs) and chlorinated pesticides that are resistant to breakdown both in the environment and in the human body. While these chemicals have been known to cause cancer and nervous system damage for many years, we now are discovering that exposure to remarkably low concentrations increases the risk of a host of additional diseases. Type II diabetes is usually thought to be a disease of obesity and inactivity. However obesity is usually a consequence of eating too much animal fat, and the animal fat contains the POPs. Studies in our and other laboratories now are finding that exposure to POPs (especially pesticides) is a major risk factor for diabetes. Lee et al. (Diabetes Care 29: 1638: 2006) found a 38-fold elevation in risk of diabetes in individuals with elevated levels of 3 pesticides, 2 dioxins and one PCB, and that obese persons with low POPs were not at elevated risk of diabetes. We have also studied hypertension and heart disease. For hypertension serum PCB levels are the greatest risk factor other than age, and even those with "normal" blood pressure show higher pressure in relation to serum PCB level, but not pesticides. Cardiovascular disease, on the other hand, is elevated more in relation to pesticide levels. These results indicate that POPs increase the risk of the major human chronic diseases by mechanisms not yet clear.