Acute, febrile disease in a young person with no previous medical history is most often caused by infection. If disease progresses despite antimicrobial treatment vascular and collagen diseases should be taken into account in differential diagnosis We present a case of a young man, with lung infiltrations and cavities in the course of febrile illness. He was referred to our hospital with a suspicion of Wegener's granulomatosis after few days of ineffective antimicrobial therapy. Positive blood culture for S. aureus and demonstration of tricuspid valve vegetation on echocardiographic examination enabled to make a final diagnosis of infective endocarditis with multiple lung abscessus.