Well-designed data management processes are essential in ensuring the quality of data collected in multicenter clinical trials. This paper describes the data management processes and systems that were developed by the data coordinating center of the Asthma Clinical Research Network. A combination of manual and electronic processes has been designed to process clinical trial data from the point of collection to statistical analysis. A distributed database management system consisting of modular applications for separate data processing activities was developed to enter, track, verify, validate, and edit collected data. In addition, processes for monitoring and reporting data quality are discussed.