A critical mass of Internet users will soon enable wide diffusion of electronic communication within medical practice. E-mail between physicians and patients offers important opportunities for better communication. Linking patients and physicians through e-mail may increase the involvement of patients in supervising and documenting their own health care, processes that may activate patients and contribute to improved health. These new linkages may have profound implications for the patient-physician relationship. Although the federal government proposes regulation of telemedicine technologies and medical software, communications technologies are evolving under less scrutiny. Unless these technologies are implemented with substantial forethought, they may disturb delicate balances in the patient-physician relationship, widen social disparities in health outcomes, and create barriers to access to health care. This paper seeks to identify the promise and pitfalls of electronic patient-physician communication before such technology becomes widely distributed. A research agenda is proposed that would provide data that are useful for careful shaping of the communications infrastructure. The paper addresses the need to 1) define appropriate use of the various modes of patient-physician communication, 2) ensure the security and confidentiality of patient information, 3) create user interfaces that guide patients in effective use of the technology, 4) proactively assess medicolegal liability, and 5) ensure access to the technology by a multicultural, multilingual population with varying degrees of literacy.