Type 1 diabetes mellitus (T1D) patients (G1; n=73) and first degree relatives with islet cell antibody (ICA) values of >or=10 JDF u twice or >or=20 JDF u one and loss of FPIR (G2; n=18) were screened for two other autoantibodies, anti-glutamic acid decarboxylase (GADA) and insulin autoantibodies (IAA), and for other organ-specific autoantibodies, anti-gastric parietal cell (anti-PCA) and anti-thyroid peroxidase (anti-TPO) as well. The two control groups consisted of healthy subjects (G3; n:55 and G4; n:13). In G1, positivity of ICA, GADA, IAA, anti-TPO and anti-PCA were 63%, 75.1%, 27.4%, 17.8% and 8.2%, respectively. In G2, positivity for GADA, IAA, anti-TPO and anti-PCA were 55.6%, 11.1%, 16.7% and 11.1%, respectively. None of the anti-TPO or anti-PCA positive cases had clinical or laboratory thyroid disease or pernicious anemia. Other organ specific antibodies, in case they accompany GADAand/or IAA in high risk individuals, result in higher risk for T1D. Moreover, this condition may indicate future potential for developing thyrogastric autoimmune diseases. In conclusion; autoantibodies are markers for autoimmune destruction in T1D, and for identification of subjects at risk for disease. Even at the time of diagnosis of T1D, screening for thyrogastric autoimmunity might be recommended for early detection of the relevant diseases.