Objective: Thrombotic microangiopathies have been increasingly recognised in HIV infection. The contribution of haemolytic uraemic syndrome (HUS) has not received as much emphasis as other members of the thrombotic microangiopathies. We describe the clinical features and prognosis of HUS in a group of patients with AIDS. Setting: St Bartholomew's and The Middlesex Hospitals, London. Patients: Five HIV seropositive individuals with clinical and histological features consistent with HUS. Interventions: Blood transfusion, fresh frozen plasma, haemodialysis, renal biopsy, autopsy. Conclusions: HUS occurs in advanced HIV infection. Hypertension was a prominent clinical feature in HUS in this patient group. Measures to limit renovascular damage were unsuccessful and haemodialysis was usually needed to support renal function. The prognosis is poor, no patient achieved clinical remission and all died.