Exposure to persistent organic pollutants (POPs) may influence telomere length (TL), which is considered as a marker of biological age associated with the risk of chronic disease. We hypothesized that dietary exposure to polychlorinated biphenyls (PCBs) and dioxins could affect TL. Our aim was to evaluate the association of dietary exposure to PCBs and dioxins with TL. In this cross-sectional study of 886 subjects older than 55 y (mean age: 67.7; standard deviation (SD): 6.1; 27% women) from the "Seguimiento Universidad de Navarra" (SUN) project. TL was determined by real-time quantitative polymerase chain reaction and dietary PCBs and dioxins exposure was collected using a validated 136-item Food Frequency Questionnaire. Multivariable linear regression models were used to control for potential confounding factors. Shorter TL was associated with dietary total PCBs (SD of T/S ratio/(ng/day) = -0.30 x 10(-7); 95% CI, -0.55 x 10(-7) to -0.06 x 10(-7)), dioxin-like PCBs (DL-PCBs) (SD of T/S ratio/(pg WHO TEQ (Toxic Equivalents)/day) = -6.17 x 10(-7); 95% CI, -11.30 x 10(-7) to -1.03 x 10(-7)), and total TEQ exposure (SD of T/S ratio/(pg WHO TEQ/day) = -5.02 x 10(-7); 95% CI, -9.44 x 10(-7) to -0.61 x 10(-7)), but not with dioxins (SD of T/S ratio/(pg WHO TEQ/day) = -13.90 x 10(-7); 95% CI, -37.70 x 10(-7) to 9.79 x 10(-7)). In this sample of middle-aged and older Spanish adults, dietary exposure to total PCBs and DL-PCBs alone and together with dioxins was associated with shorter TL. Further longitudinal studies, preferably with POPs measured in biological samples, are needed to confirm this finding.