Centralized patient registration and treatment randomization for multicenter clinical trials has many advantages over other approaches. Our Automated Patient Registration and Treatment Randomization system is a fully automated Interactive Voice Response, microcomputer-based application which can operate unattended and is continuously available to provide patient registration and treatment randomization. Several techniques are employed to ensure security of the system and validity and accuracy of the data. Several randomization methods were implemented to support different study designs including balanced block randomization, stratified permuted block scheme, and a sophisticated randomization design based on the minimization method and Zelen's adaptive randomization method for institution balancing.