In order to identify the characteristics of patients with hematological malignancies (HM) in the presence/suspicion of any accompanying infectious disease, and to find the predictors of mortality in this group, hospital charts of patients with HM consulted by the Infectious Diseases (ID) team for signs/symptoms of any infection between January 1, 1997 and December 31, 2001 were retrospectively reviewed. A total of 1,132 consultations were done for 641 patients: 59.4% of the patients were male and the mean (+/- standard deviation) age of the study participants was 47.9 +/- 1.4 years. The most common underlying diseases were non-Hodgkin's lymphoma (30.9%), acute myelogenous leukemia (26.2%), and multiple myeloma (10.9%). Clinically and microbiologically documented infections and fever of unknown origin were observed in 43.3%, 38.1%, and 18.5% of the participants, respectively. Bloodstream infections were detected in 134 episodes (20.9%): 56.5% were caused by gram-negative microorganisms. In logistic regression analysis, the presence of pneumonia (OR 7.56, 95% CI 4.84-12.486), invasive fungal infection (OR 4.12, 95% CI 1.78-9.55), relapse or recent diagnosis of the underlying disease (OR 2.82, 95% CI 1.53-5.21) and neutropenia (OR 2.70, 95% CI 1.70-4.31) were identified as statistically significant predictors of mortality.