Antibodies recognising different pancreatic autoantigens (Abs) are detected many years before the clinical onset of insulin-dependent diabetes mellitus (IDDM). The humoral immune alterations, observed in the susceptible subjects, for example in first degree relatives of IDDM patients, could serve as predictive markers of IDDM development. It has recently been suggested that the predictive value of these humoral markers is associated with the number of the studied antibodies directed against different pancreatic antigens (ICA, GADA, IA-2,A IAA). The aim of the study was the estimation of the prevalence and titre of the antibodies directed against protein tyrosine phosphatase-2 (IA-2) and glutamic acid decarboxylase (GAD) in patients with newly diagnosed diabetes type 1 and their first degree relatives. The investigations were carried out in 52 diabetics (aged 5-25 years) and 136 first degree relatives. IA-2A and GADA were performed by radiobinding assay (RIA) using 2 microliters of serum and recombinant S35-labelled GAD65 and IA-2 antigens. The threshold of Abs detection was > or = 97.5 centile (of healthy schoolchildren). At least one of the antibody marker was detected in 92.7% of newly diagnosed IDDM patients, slightly more frequently observed were GADA (78.8%) than IA-2A (71.2%). The presence of 2 types of antibodies was found in 8.7% of parents and 9.4% of the siblings. The results of our study confirm high sensitivity and specificity of the combined measurement of IA-2A and GADA in recognising of autoimmune alterations in diabetes type 1 development. Taking into consideration small volume of the serum suitable for Abs measurement and possibility of the combined estimation of these Abs it seems that IA-2A and GADA combined measurement could actually serve as a screening marker for the detection of high risk of IDDM subjects also in the Polish population, but studies concerning their predictive value in the general population are suggested.