OBJECTIVE: Computer-assisted telephone interviewing (CATI) systems used by telephone counselors (TCs) may be efficient mechanisms to counsel patients on cancer and recommended preventive screening tests in order to extend a primary care provider's reach to his/her patients. The implementation process of such a system for promoting colorectal (CRC) cancer screening using a computer-assisted telephone interview (CATI) system is reported in this paper. METHODS: The process evaluation assessed three components of the intervention: message production, program implementation and audience reception. RESULTS: Of 1181 potentially eligible patients, 1025 (87%) patients were reached by the TCs and 725 of those patients (71%) were eligible to receive counseling. Five hundred eighty-two (80%) patients agreed to counseling. CONCLUSIONS: It is feasible to design and use CATI systems for prevention counseling of patients in primary care practices. PRACTICE IMPLICATIONS: CATI systems have the potential of being used as a referral service by primary care providers and health care organizations for patient education.