Background: The efficacy and safety of rituximab(R)-based immunochemotherapy, the standard regimens for patients (pts) with diffuse large B-cell lymphoma (DLBCL) which is more common in Asia than in Western countries, are well confirmed in RCT studies. However, the safety and effectiveness of R+chemo for DLBCL in real world use is not widely reported, especially population are normally excluded in RCT studies. The objective of this observational study is to investigate the safety and effectiveness of R+chemo as 1st line treatment for Chinese DLBCL in routine clinical practice. Methods: This study was a multicenter, prospective, single-arm observational study conducted in China. DLBCL pts eligible to receive R+chemo (CHOP or non-CHOP) as 1st line treatment were enrolled with no specific exclusion criteria. The primary endpoint was safety. Data on safety and effectiveness were collected from medical records 120 d after the last R dose was administered. This study was registered in clincialtrials.gov (NCT01340443). Results: In total, 279 pts (162male/117femal) with a median age of 57 yrs (range 13 to 88 yrs) were included in the safety analysis set. By IPI criteria, 50.2% of pts were low risk, 25.4% low-intermediate risk, 16.5% intermediate-high risk, 7.2% high risk and 0.7% with unknown risk. The most common concomitant diseases observed are liver (44,15.8%), heart (23, 8.2%), kidney (9, 3.2%) or lung (7, 2.5%) disease. Pts received R+chemo treatment with a median cycle of 6 and a median interval of 24 d. In total, 52.7% pts had grade 3-4 AEs and 16.8% pts had SAE (Table 1). AE related death was 1.1% (n=3). 67.0% pts had any grade hematologic toxicity and the most common grade 3/4 hematologic toxicities were leukocytopenia (29.7%), erythrocytopenia (3.9%), and thrombocytopenia (5.7%). Infection (46.2%), gastrointestinal toxicity (45.2%), and liver toxicity (12.5%) were common non-hematologic toxicities. The AEs of special population (with common concomitant and very young/older DLBCL) are listed in Table 2. For HBV management, the incidence of HBV reactivation in HBsAg+, HBsAg-/HBcAb+, HBsAg-/HBcAb-, and undefined pts was 12.5% (3/24), 4.3% (3/69), 0.7% (1/149), and 2.7% (1/37), respectively, no death due to HBV reactivation 120 d after the last R dose was administered. The detail outcomes of HBV reactivation management in this study was reported in EHA 2014. For ITT population (n=258), the overall response rate was 93.7%. Rates of complete response (CR), unconfirmed CR (CRu) and partial response (PR) were 55.0%, 18.2% and 20.9%, respectively.