BACKGROUND: The antiphospholipid antibodies have been characteristically found in the patients with autoimmune diseases. Some previous studies revealed that antiphospholipid antibodies are increased in the sera of patients with diabetes and correlate with the extent of neuropathy and measurements of amiphospholipid antibodies may constitute a marker for ongoing damage to nerves. We measured serum anticardiolipin antibodies(IgG, IgM) to assess the prevalence and significance of anticardiolipin antibodies in NIDDM patients. METHOD: Ninety NIDDM patients were screened for lgG/IgM isotypes of anticardiolipin antibodies by enzyme-linked immunosorbent assay and compared with 30 control subjects. RESULTS: 1) The titers and positivities of IgG anticardiolipin antibodies were significantly higher in the sera of NIDDM patients than those of control subjects(P<0.05). 2) In NIDDM patients with IgG anticardiolipin antibody, the titer of serum c-peptide was significantly lower(P<0.05) and the body mass index tended to be lower(P=0.08). 3) There were no significant differences of positivities of IgG anticardiolipin antibodies according to the state of chronic diabetic complications and the mode of treatment(P>0.05). 4) In the patients with NIDDM, no significant association was found between the titers of IgG anticardiolipin antibodies and age, diabetic duration, fasting blood glucose, HbAlc, total cholesterol and triglyceride. CONCLUSION: The titers and positivities of IgG anticardiolipin antibodies were elevated in NIDDM. In the NIDDM patients with IgG anticardiolipin antibody, the serum titers of c-peptide were significantly lower and the body mass index tended to be lower. It seems that serum IgG anticardiolipin antibodies might have autoimmune relationship with slowly progressive IDDM, but further prospective mass studies will be requird.