IgG and IgM anticardiolipin antibody (Ab) concentrations were determined in serum samples of 48 children with end-stage renal disease (ESRD) on haemodialysis using ELISA technique in an attempt to analyse their possible role in the occurrence of thrombosis of the vascular access. Ten normal healthy children were studied as a control group. The positivity of anticardiolipin Ab isotypes both IgM and IgG was high in children with ESRD on haemodialysis. Children with positive anticardiolipin Ab had significantly higher incidence of prior thrombosis of vascular access. Also, these antibodies should be considered as markers of high risk for fistula thrombosis.