OBJECTIVE: The aim of the study was to assess thyroid function, iodine intake and exposure to dietary goitrogens of children living in an area with a high prevalence of goitre, in the region of Darfur, Sudan. DESIGN: In a village where goitre affected approximately 85% of children, a cross-sectional survey of thyroid function was performed in children 0-7 years old. PATIENTS: Twenty neonates and 190 children, aged 1 month to 7 years, were included. MEASUREMENTS: Thyroid hormones, urinary iodide and thiocyanate excretion were measured. RESULTS: Mean +/- SD serum T4 was below the normal range at birth (82 +/- 50 nmol/l) and in the age group less than 2 years (73 +/- 46). Children older than 2 years had even lower serum T4: 37 +/- 37 (P < 0.001) at 3-4 years and 36 +/- 38 (P < 0.001) at 5-7 years. Mean serum TSH was 25.8(6.2-107.7) mU/l at birth, 8.3(2.5-27.8) in the group less than 2 years, 15.3(2.9-79.1) at 3-4 years and 16.4(2.7-98.3) at 5-7 years. The overall prevalence of hypothyroidism (TSH > 50 mU/l) was 24%. Mean urinary thiocyanate was high at birth (107 +/- 69 mumol/l), normal in the group less than 2 years and higher in children older than 2 years (126 +/- 69 mumol/l) (P < 0.001). All age groups had a low urinary iodide concentration. CONCLUSION: Hypothyroidism was very frequent in each age group. The higher frequency of hypothyroidism observed in weaned children (> 2 years) was attributed to the combined effects of iodine deficiency and goitrogens (thiocyanate and glycosylflavones) derived from millet.