Non-Hodgkin's lymphoma (NHL) includes lymphoproliferative malignant diseases with a wide variety of clinicopathologic appearances. The aim of our study was to analyse the critical prognostic factors that effect clinical picture in NHL patients. In this study, we retrospectively evaluated the effects of the clinical characteristics, International Prognostic Index (IPI) parameters (age, stage, performance status, extranodal sites, and serum lactate dehydrogenase), and other prognostic parameters (bulky disease, grade of disease, "B" symptoms, and beta-2 microglobulin levels) on overall survival (OS) and disease-free survival (DFS) in NHL patients who have been diagnosed in our department. Stage of the patients was not related with OS and DFS. But higher grade and IPI levels were found to be independent prognostic factors that predict OS. According to clinical and laboratory parameters, only age and bulky disease were found to be an independent risk factor that predict OS. In conclusion, our results suggest that, using only the stage and/or grade of the disease does not completely correlate with the prognosis. Stage and grade could be significant indicators, if they are evaluated along with other prognostic factors.