OBJECTIVES: In China, an estimated 90 million adults are diabetic. An out-patient clinic physician in a comprehensive hospital sees an average of 50 patients per day. Patients but not physicians maintain the medical records. Investigators are not used to electronic data acquiring systems. All these factors present challenges for conducting quality outcomes research. We recently conducted “Nationwide Assessment of Cardiovascular Risk Factors in Chinese Patients with Type 2 Diabetes”, which was aimed to enroll 25000 non-institutional patients nation-wide. In order to ensure high quality and efficiency of the study, a multifaceted data quality control process was implemented and evaluated. METHODS: For enrolled patients who signed informed consent form, investigators were first required to report the original patient information on a “Patient Record Form” which served as source documents, and subsequently to enter the data into a web-based electronic data capture system (VitalEDC, VSRI), which performs instantaneous edit checks and generates real time data query. All investigational sites received frequent onsite monitoring and auditing when frequent data query occurred or when 50% enrollment achieved. Additionally, a 10% of the patient records at each site were randomly selected for a remote source document verification (rSDV). RESULTS: A total of 734 investigators from 103 hospitals across 6 regions of China participated in this study, and 25817 patients were enrolled within 8 months. Among enrolled patients, 100% the data were retrieved, 4,590,00 data records were evaluated, over 3000 unique queries were generated, only 1.5% (377 out of 25,817) of the patients’ records were excluded from analyses due to unexplainable queries of pre-defined key information. CONCLUSIONS: The large sheer volume and rising epidemic of cardiometabolic and other chronic diseases demand well controlled epidemiological and comparative effectiveness research in China. Despite challenges, multifaceted measures of quality control could yield relatively satisfactory outcomes.