The degree of infection and the urographic picture was correlated to the presence and level of circulating immune complexes (CICs) in 69 patients affected by urinary schistosomiasis. Patients were divided into 2 groups: those eliminating less and those eliminating more than 25 eggs/10 ml of urine. Radiological changes in the urinary tract were present in 67% of patients, the most frequent finding being single or multiple filling defects in the bladder. CICs were present in 39 patients. A positive correlation was found between the presence and level of CICs and the output of Schistosoma haematobium eggs, as well as between the presence of CIC and single or multiple filling defects of the bladder. Our findings indicated that CICs were present in patients with urinary schistosomiasis, but the different incidence in patients with a large egg output and radiological filling defects suggests a possible pathogenic role only in the earlier phase of the infection.