The association of a polychlorinated dibenzo-p-dioxin, a polychlorinated biphenyl, and p,p'-DDT with diabetes was evaluated using the 1999-2002 National Health and Nutrition Examination Survey. Persons 20 years old and older were included. Relationships with diagnosed diabetes, undiagnosed diabetes (glycohemoglobin (HbA1c) >6.1%), and total diabetes (diagnosed plus undiagnosed) were tested. When all three chemicals were evaluated together for total diabetes, the unweighted number of participants was 1830. All three compounds were significantly associated with diagnosed diabetes. PCB 126 and p,p'-DDT were significantly associated with undiagnosed diabetes. 1,2,3,6,7,8-hexachlorodibenzo-p-dioxin (HxCDD) was not associated with undiagnosed diabetes. When the three chemicals were included in a combined model for total diabetes, PCB 126>83.8pg/g lipid adjusted had an odds ratio of 2.57 (95% CI 1.33-4.95) compared to PCB 126 < or = 31.2pg/g lipid adjusted. Also significant in a combined model for total diabetes was p,p'-DDT 20.8-26.6ng/g lipid adjusted with an odds ratio of 2.52 (95% CI 1.26-5.02) and p,p'-DDT >26.6ng/g lipid adjusted with an odds ratio of 2.74 (95% CI 1.44-5.23) both compared to p,p'-DDT < or = 20.7ng/g lipid adjusted. HxCDD was not associated with total diabetes in a combined model. When participants with poor liver function and poor kidney function were removed from the analysis, the combined model for total diabetes produced similar results with PCB 126 and p,p'-DDT having been significantly associated, and HxCDD not having been associated. These findings add to the list of chemicals found to be associated with diabetes in the 1999-2002 National Health and Nutrition Examination Survey.