Management of acute renal failure (ARF) in an intensive care unit (ICU) is difficult. The aim of this study was to identify prognostic factors determining ARF outcome in the ICU in terms of dialysis dependency or independency. We included 35 patients who turned out to be dialysis dependent (DD) and 11 patients who turned out to be dialysis independent (DI) after ARF in the ICU, which necessitated renal replacement therapy. In the post-ARF period, acetylsalicylic acid was protective against dialysis dependency (p < 0.05, odds ratio [OR] = 0.078) and dopamine increased the likelihood of dialysis dependency (p = 0.016, OR = 10.6). Multiorgan dysfunction (p = 0.001, OR = 13.6), especially cardiac (p = 0.009) and hepatic failure (p < 0.0001) were determined to increase risk of dialysis dependency. Mean systolic blood pressures during the first 24 hours (p = 0.023) and 24-48 hours (p = or < 0.0001), mean diastolic blood pressures during first the 24-48 hours (p = 0.03) and 48-72 hours of ARF in ICU (p = 0.023) and at discharge (p = 0.03) were significantly lower in the DD group than in the DI group. Mean thrombocyte counts at hospitalization (p = 0.034), during the first 24 hours (p = 0.019) and 24-48 hours of ARF in ICU (p = 0.038) were lower in the DD than DI group. This study demonstrates the very early prognostic factors influencing ARF outcome in terms of dialysis dependency. Early thrombocyte count and systolic blood pressure and follow-up diastolic blood pressure were prognostic factors for ARF outcome. Acetylsalicylic acid seemed to improve renal outcome, whereas dopamine seemed to worsen the disease process.