BACKGROUND: This study was designed to evaluate radiological findings in chest and sinus radiographs and renal ultrasound (US) in patients with nephropathia epidemica (NE) and to determine whether changes in these medical images are related to each other or to the clinical course of NE. METHODS: Radiological findings and clinical course were studied in 380 hospital-treated NE patients during the years 1982-1998. RESULTS: In 35% of the patients there were clear changes in chest radiographs. Pleural effusion, atelectasis, and interstitial infiltration were the most common X-ray findings. Forty-seven percent had changes in renal US, with increased cortical echoicity and cortical swelling being the most common findings. Thirty-three percent of the patients with clinical symptoms of sinusitis had changes in sinus radiographs. Abnormal findings on chest radiographs were clearly associated with fluid volume overload, high blood pressure level, leukocytosis, degree of clinical renal insufficiency, and thrombocytopenia. Abnormal findings in renal US were associated to some extent with fluid volume overload and degree of clinical renal insufficiency. CONCLUSIONS: Some 35% of patients had clear changes in chest radiographs and 47% showed changes in renal US. Abnormal findings in chest radiographs were clearly associated, and abnormal findings in renal US were associated to some extent, with the severity of the clinical course of NE.