Anticardiolipin antibodies (ACA) have been described in association with thrombosis and several vascular diseases and may be involved in retinal vasculitis. To investigate this question we tested sera from 86 patients with posterior uveitis and 100 healthy controls for the presence of anticardiolipin antibodies. The antibody was present in 15 patients: in 7 of the patients with acute retinal necrosis (n = 24), in 4 with idiopathic retinal vasculitis (n = 10), 3 with syphilis (n = 6) and in one SLE patient with retinal vasculitis.Ten patients had IgA-type anticardiolipin antibodies, 6 had IgM-type and 4 had IgG-type anticardiolipin antibodies. Anticardiolipin antibodies could not be detected in sera from uveitis patients with Behcet's disease (n = 10), sarcoid (n = 9), toxoplasmosis (n = 7), multiple sclerosis (n = 3) or Birdshot chorioretinopathy (n = 10). Ten of the healthy controls had cardiolipin antibodies of the IgM class.The exact role of these auto-antibodies in the pathogenesis of retinal vasculitis remains to be resolved.