There is some evidence that leukocytosis without infection is associated with increased hospital mortality, but data in this regard are very incomplete. This study was designed to investigate the relationship between leukocytosis at the time of admission and mortality among patients hospitalized in general wards. During July to Nov 2004, all deceased patients who had a white blood cell (WBC) count record for the first 24 hours of admission were selected as cases. Among survivors, twice the number of cases was selected as controls. Different levels of WBC counts were compared between cases and controls. Totally 1650 patients, including 550 deceased (cases) and 1100 survivors (controls) were analyzed. Of these, 876 (53%) were males and 774 (47%) females, and 42 (3%) were admitted to ICU, 1426 (86%) to medical and 182 (11%) to surgical wards. There was a significant difference between the mean age of deceased patients (78.0 years) and survivors (53.0 years) (P10×109/l accounted for 804, among which 335 (42%) were deceased. Leukocytosis and leukopoenia were more frequent among the deceased patients compared to the survivors. The likelihood ratio for leukocytosis and leukopenia among the cases and controls was 1.4 and 2.3, respectively. Leukocytosis was identified as an alarming sign for mortality among patients admitted to general hospital wards at early stages of admission. A quick medical intervention for amendment of the causes related to leukocytosis should consequently reduce hospital mortality.