Objectives: To evaluate potential changes of infective endocarditis (IE) in patients treated in a Finnish teaching hospital during the past 25 years. Patients: 326 episodes of IE in 303 patients treated during 1980-2004 were evaluated for clinical characteristics and their changes over time.Results: The mean age of the patients increased with time (from 47.2 to 54.5 years, p = 0.003). Twentyfive (7.7%) episodes were associated with intravenous drug use (IVDU), with a significant increase of these episodes after 1996 (from 0 to 19 (20%), p , 0.001). Viridans streptococci were the most common causative agents of IE during 1980-1994, but after that Staphylococcus aureus was the most common pathogen (p = 0.015). The proportion of IE of the aortic valve decreased during the study (from 30 (49%) to 26 (27%), whereas the proportions of mitral (11 (18%) to 33 (35%) and tricuspid valve IE (0 to 13 (14%) increased correspondingly (p = 0.001). This was mainly due to more patients with IVDU. Chronic dialysis for renal failure as an underlying condition increased over time (from 0 to 7 (7.4%), p = 0.015) but no other predisposing conditions changed. Complications such as neurological manifestations and heart failure did not change in frequency, but the incidence of lung emboli increased (from 0% to 10.5%, p , 0.001); 83% of these emboli occurred in patients with IVDU. The proportion of patients requiring surgical treatment and mortality due to IE did not change. Conclusions: During these 25 years, the causative agents, affected valves and complications of IE changed to some degree. These changes were mainly attributed to the increase of IVDU-associated IE. Except for the increase in age, the clinical presentation and outcome in non-addicts remained substantially unchanged.