Background: Uremic patients on hemodialysis (HD) often display occlusive disorders despite their uremic thromboasthenia. The role of anticardiolipin antibodies (aCL) and the recently identified anti-β<sub>2</sub>-glycoprotein I antibodies (aβGPI) in these phenomena is unknown. Methods: The prevalence of IgG and IgM aCL and aβGPI was documented in 54 HD patients and 19 nondialyzed patients with chronic renal failure (CRF). The HD patients were further divided into arteriovenous (AV) access occluders and nonoccluders. Results: HD patients had a higher mean IgG aCL level than CRF patients (14.68 ± 3 vs. 2.96 ± 1 IU/ml, respectively, p < 0.0007). IgM aCL did not differ significantly. AV access occluders had a higher mean IgG and IgM aCL levels than nonoccluders (24.47 and 8.39 IU/ml in occluders vs. 8.45 and 3.59 IU/ml in nonoccluders, p < 0.0226 and p < 0.05, respectively). IgM and IgG aβGPI antibody levels were below the cutoff point and did not differ significantly between the various groups. Cardiovascular episodes were not correlated with the titer of aCL or aβGPI. Conclusion: These results indicate that HD, especially in patients with recurrent access occlusion episodes, is associated with elevated levels of IgG aCL, and that IgG aCL level may predict the occlusive status of HD patients.