17557 Background: Natural Killer (NK) cell lymphoma is a group of increasingly recognized but poorly defined disease entities. This study investigated its clinical features and prognostic factors for southern China population. METHODS Patients with pathologically confirmed NK cell lymphoma in one center since 1999 to 2004 were included. Central histological and immunohistochemical review was undertaken to every case. The major study endpoint was overall survival. Survival curves were estimated by the Kaplan-Meier method. Detailed clinical, pathological and laboratory data were included in univariate analysis and statistically significant factors in univariate analysis were then included in multivariate analysis. RESULTS Totally 64 eligible patients were identified. Of these, 59 patients were extranodal NK cell lymphoma nasal type, 3 patients were aggressive NK cell lymphoma and 2 patients were blastic NK cell lymphoma. From the basic analysis, 47% of the patients had stage I disease, 42% were stage II, 11% were stage III or IV. B-symptoms were present in 39%. 73% of these patients had International Prognostic Index (IPI) 0 or 1. Before treatment, 25% complicated with anemia. As to the therapy, 38% received chemotherapy alone, 3% received radiotherapy alone and 59% received a multidisciplinary therapy. After initial therapy, 59% achieved CR, 22% achieved PR and 19% were refractory disease. With a median follow-up duration of 20 months, the median overall survival was 28 months (95% CI: 10, 45). Hb lower than 110 g/l before treatment was statistically significant in multivariate analysis (p = 0.031). Presenting B-symptoms and ECOG PS score higher than 1 were also independent prognostic factors (P = 0.001 and 0.006 respectively). CONCLUSIONS The outcome of patients with NK cell lymphoma was poor even for Stage I or II cases. Our data suggested Hemoglobin < 110 g/l had more prognostic value than IPI and Ann Arbor staging system for NK cell lymphoma in southern China, but it needs further confirmation. No significant financial relationships to disclose.