Anti-endothelial cell antibodies (AECA) have been found to play an important role in many vascular disorders. In order to determine the presence of AECA in children with Henoch–Schönlein purpura (HSP), and to elucidate the pathogenic and clinical value of their measurement in this disease, AECA were detected by immunofluorescence staining and a human umbilical vein endothelial cell (HUVEC)-based enzyme-linked immunosorbent assay (ELISA) in 20 children with HSP, 10 children with juvenile rheumatoid arthritis (JRA) without vasculitis and 10 normal healthy children. Antibodies against another endothelial cells, human dermal microvascular endothelial cells (HMVEC-d) were also detected by cell-based ELISA. In some experiments, we compared the binding activity of antibodies to HUVEC with and without tumour necrosis factor-α (TNF-α) or interleukin-1 (IL-1) pretreatment. Patients with acute onset of HSP had higher serum levels of IgA antibodies, both against HUVEC and against HMVEC-d, than healthy controls (P = 0·001, P = 0·008, respectively). Forty-five per cent of patients had positive IgA AECA to HUVEC, and 35% had positive IgA AECA to HMVEC-d. The titres of IgA antibodies to HUVEC paralleled the disease activity. After TNF-α treatment, the values of IgA AECA to HUVEC in HSP patients were significantly increased (P = 0·02). For IgG and IgM AECA, there was no difference between HSP patients and controls (P = 0·51, P = 0·91). Ten JRA children without vasculitis had no detectable IgG, IgM or IgA AECA activity. The results of this study showed that children with HSP had IgA AECA, which were enhanced by TNF-α treatment. Although the role of these antibodies is not clear, IgA AECA provide another immunological clue for the understanding of HSP.