Objectives: Arteriovenous fistula (AVF) is Achilles hill of patients receiving maintenance hemodialysis, but thrombosis of AVF is a frequently encountered problem in maintenance hemodialysis patients. AVF thrombosis or occlusion is known to be associated with old age, underlying diabetes mellitus, increased fibrinogen and factor VIII, short AVF maturation time, low dialyzer blood flow, etc. Recently, several reports suggested that high titer of IgG anticardiolipin antibody (IgG-ACA) is associated with single or repeated clotting of AVF and elevated Lp(a) level is associated with vascular access occlusion in patients under maintenance hemodialysis. This study is to investigate the relationship between AVF thrombosis and the presence of elevated titiers of LP (a) and IgG-ACA. Methods: This study included 20 patients with end stage renal disease under hemodialysis via AVF. Ten subjects have had one or more episodes of AVF obstruction (group A). Another 10 subjects without episodes of AVF obstruction (group B) were selected matching with age, sex, underlying disease, duration of hemodialysis, blood glucose level and lipid profile of subjects in group A. The IgG, IgM anticardiolipin antibody titers with indirect ELISA method and LP (a) level with turbidimetric assay were measured and analysed. Results: Four subjects in group A showed positive IgG-ACA titer what of all subjects in group B were negative titer (p=0.03). Only one subject in group A and two subjects in group B showed positive IgM-ACA titer (p>0.05). The median value of Lp (a) was 32.75 (mg/dl), 43.1 (mg/dl) in group A and group B respectively and was not significantly different each other (p>0.05). Conclusions: In end stage renal patients receiving hemodialysis, positive IgG-ACA titier seems to be an independent risk factor of AVF thrombosis.