Introduction: Acute renal failure (ARF) is a serious complication that occurs in 5%-18% of hospitalized patients and in up to 30% of patients admitted to Intensive Care Unit. The hospital mortality rate of patients with ARF is between 28% and 90%. The incidence of ARF is proportional to patient age. Therefore, despite all improvements in modern medicine, the annual incidence of ARF has not changed over the two past decades. The aim of our study was to analyze the incidence and causes of ARF in our Center during the five-year period, to analyze the characteristics of patients and their comorbid conditions, variations in laboratory parameters during hospitalization, and therapy administered. Also, we analyzed the outcome and length of hospitalization. Subjects and Methods: During the five-year period (from January 2008 till December 2012), we analyzed 316 patients treated for ARF at Department of Nephrology and Dialysis, Rijeka University Hospital Center. Data were obtained by searching medical records. ARF was defined according to the KDIGO recommendations: increase in serum creatinine (sCR) >26 μmol/L within 48 h, or increase in sCR by 1.5 times compared to the reference values , which is known or assumed to have appeared within a week of hospitalization, or diuresis <0.5 mL/kg/h for ≥6 hours. Results: Out of 316 ARF patients analyzed, 57 were hospitalized at our Department in 2008 (50.9% of men and 49.1% of women), 56 in 2009 (39.3% of men and 60.7% of women), 66 in 2010 (55.3% of men and 44.7% of women) and 76 in 2011 (55.3% of men and 44.7% of women). In 2012, we analyzed 61 ARF patients (42.6% of men and 53.4% of women). There were no statistically significant age and gender differences, although we noticed an increasing tendency in the number of elderly patients hospitalized for ARF. Furthermore, analyzing the frequency of patient arrival from home, nursing home or transfer from other departments we recorded an increase in the arrival of patients from nursing homes during the study period. Analysis of the proportion of patients hospitalized for ARF in our Department in relation to the total number of hospitalized patients revealed that ARF was the cause of hospitalization in 8.2%-9.9% of all patients. There was no significant change in the number of patients hospitalized for ARF during the period observed. Analyzing the frequency of hospitalization due to ARF by months, we noticed that the largest number of patients were hospitalized during summer months (from June to September). The most common form of ARF was prerenal (56.1%-67.9%). The largest number of patients were treated by parenteral rehydration and antibiotics (52.6%-71.4%). Renal replacement therapy was performed in 12.5%-21.1% of all patients. The mortality rate throughout the period of observation ranged from 21.2%-30.4%. Furthermore, complete recovery of renal function was achieved in 30.5%-40.4% of all patients. The mean length of hospital stay ranged from 11.8 to 15.1 days. Conclusion: Acute renal failure is a significant cause of hospitalization, especially in elderly patients. Therefore, early identification along with appropriate and early treatment of patients with ARF is needed to improve survival and recovery of renal function in these patients.