Insulin dependent diabetes mellitus (IDMM) is often associated with autoimmune thryroiditis (AIT) and a high prevalence of thyroid antibodies (TA). Ultrasound imaging of the thyroid may contribute to the evaluation of patients with AIT. We therefore investigated ultrasound findings of the thyroid in 83 IDDM patients (44F, 39M) with an age range of 2.3-22.3 yrs (median 11.1). Thyroid volume (ml) determined by ultrasound ranged between 1.3 and 17.9 (median 5.7). Thyroid volumes of 75 healthy children (32F, 43M) with an age range of 2.0 to 11.8 yrs (median 7.6) ranged between 1.6 and 13.2 ml (median 4.8) and did not show a significant difference from the IDDM group from age 4 to 12. TA were positive in 18.8% of the IDDM group. Thyroid volume was higher in TA (+) diabetics (p=0.05), a finding which may be attributed to a higher percentage of cases with elevated TSH in the TA (+) group. Two diabetic patients showed non-homogeneous hypoechogenecity in the ultrasound compatible with AIT which was later confirmed in one of these cases by aspiration biopsy. Ultrasound imaging of the thyroid may contribute to the evaluation of patients with AIT in IDDM.