A high incidence of autoimmune Type 1 diabetes mellitus (DM) has been clearly established in Sardinia. Although systematic epidemiological studies are still not available, an increased prevalence of thyroid autoantibodies (ATA) has been documented in the Sardinian adult population as compared to other Italian regions, suggesting that thyroid autoimmune disease may also have increased. We carried out a preliminary study with the aim of determining the prevalence of serological markers of thyroid (anti-thyroperoxydase antibodies, TPOAb) and islet cell (ICA) autoimmunity in a large number (no.=2249) of sera obtained from cord-blood of Sardinian pregnant women at delivery. The prevalence of TPOAb was 11.9%, while ICA were detected in 59 cases (2.6%). A higher prevalence of TPOAb (6/17=35.3%) was found in sera with high ICA titers (> or = 20 JDF-U), as compared to sera with low ICA titers (5-19 JDF-U) and to ICA-negative sera (3/42=7,1%; chi2=5.4, p=0.02 and 258/2190=11,8%; chi2=6.8, p=0.009 respectively). Fourteen women (all ICA-negative) were diabetic: 4 had Type 1 and 10 had gestational DM; due to the low number, no correlation could be established between DM type and TPOAb prevalence and/or titer. These preliminary data indicate that ATA are frequently observed in the general population of Sardinian pregnant women at term. As a consequence, even the frequency of postpartum thyroiditis is expected to be high. Although ATA were not increased in women with clinical overt diabetes, a higher prevalence of ATA was found in women with high titers of circulating ICA. Our results also confirm that Sardinia represents, perhaps for its peculiar genetic characteristics, an ideal place to study organ-specific autoimmunity.