Circulating immune complexes (CIC) were detected by a solid-phase Clq-binding radioassay in 13.7% of 73 insulin-dependent diabetics (IDD) as compared to 8.6% of 35 nog-insulin dependent diabetics (NIDD) and 8.3% of 24 control subjects. Islet cell antibodies (ICAb) were detected by the indirect immunofluorescent method in 31.5% of 73 IDD as compared to 8.6% of 35 NIDD and 0% of 24 control subjects. A significant correlation between the incidence of CIC and the incidence of ICAb in IDD was detected and this is in support to the concept that islet cell antibodies are involved in the formation of CIC. The possible role of immuno-pathological mechanism that might involved of IDD is discussed on the base of the significant correlation detected between CIC and ICAb on one hand, and positive diabetic family history, high levels of fasting blood sugar and low levels of fasting insulin level, on the other hand, in Saudi IDD.