From January 1984 to April 1987, we have prospectively studied 210 consecutive episodes of bacteremia recorded in patients who underwent major surgical procedures. The incidence rate was 6.4 episodes/1000 surgical procedures. Men were responsible of 73.8% of episodes. The highest incidence was recorded in general surgery patients and the lowest in Ob & Gyn patients. Bacteremia-related mortality was 15.2% (overall mortality 29.5%). The five most common microorganisms isolated were: Staphylococcus epidermidis (17.7%), Staphylococcus aureus (14.7%), polymicrobial flora (13.3%), Escherichia coli (11.4%) and Pseudomonas sp. (9.5%). The common sources of bacteremia were intravascular devices (34.7%), surgical wound infection (28.5%) and urinary tract infection (12.8%). Multivariant analysis identified six variables that influence an adverse prognosis: complications, source of sepsis in a joint or unknown, admission in trauma or vascular surgery department, development of sepsis between the second and eight postoperative day, chronic illness or fatal underlying disease and sepsis after clean surgical procedures.