Thyroid nodules were assessed by ultrasound in 3 621 presumably healthy free-living French subjects participating in the SU.VI.MAX cohort (2 160 females aged 35-60 years and 1 461 males aged 45-60 years). Urinary iodine was measured in all participants in random morning urine samples. Nodular thyroid structures ranging from 3 mm to 57 mm in diameter were found in 14.5% of the population, without significant differences between regions in the different age and sex groups. Single nodules and multiple lesions were found in, respectively, 9.7% and 3.1% of the subjects. In females, nodules increased from 12.9% to 19.2% between 35-45 years and 45-60 years, respectively (p<0.001). Thyroid nodularity was more frequent among women aged 45-60 years than among men of those ages (19.2% vs. 11.0%, p=0.001). Descriptive data provided by ultrasound differentiated the nodules into solid (43.4%), cystic (38.4%), and mixed solid-cystic (18.2%). Most solid thyroid nodules, 76.1%, were hypoechoic, while 16.6% were iso-, and 7.3% were hyperechoic. The median of iodine concentrations (n=3 276) was 8.0 microgram/100 ml, with 19.4% of the samples being<5 microgram/100 ml. Median iodine concentrations displayed wide regional variations, with values significantly higher in residents of western regions than among those living in the eastern areas (p<0.001), independently of age and sex. No relationship was found between prevalence of nodular thyroid structure and the state of borderline iodine status observed in France.