A recent study by Rier et al. showed that rhesus monkeys exposed daily for 4 years to 5 or 25 ppt of dioxin in food develop endometriosis, with incidence and severity related to dose. We aimed to determine whether the total time-integrated dioxin exposure of a human population could be comparable to that of Rier's monkeys. We selected a sample of residents of Seveso, Italy, who were acutely exposed to high levels of dioxin following an accident in 1976. We conducted a toxicokinetic analysis which takes into account species and exposure differences in dose and timing between humans and monkeys. The area under the time-concentration curve for dioxin in fat, which corresponds to cumulative exposure over time, ranges for some of the most heavily exposed Seveso residents from approximately 1.7 x 10(6) ppt-days to 1.1 x 10(8) ppt-days. These values exceed in all cases the values for the monkeys exposed to 25 ppt or 5 ppt. Given their exposure, the Seveso population should be an ideal epidemiologic cohort to rule out or confirm whether exposure to dioxin leads to an increased risk of endometriosis in humans.