A hospital-based matched case-control study was conducted in order to identify risk factors for the development of bloodstream infections in adult hospitalized patients. Between January 1993 and December 1994, 264 episodes of bloodstream infection were evaluated. Significant variables identified by univariate analysis were included in a multivariate model that showed that central venous catheter [odds ratio (OR), 6.71], poor performance status (OR, 3.40), weight loss (OR, 2.47), hematologic diseases (OR, 2.24), and previous antimicrobial therapy (OR, 2.12) independently influenced the outcome. The knowledge of modifiable risk factors is useful in the development of strategies that may contribute to the prevention of bloodstream infections.