Secure e-mailing between Kaiser Permanente physicians and patients is widespread; primary care providers receive an average of 5 e-mails from patients each workday. However, on average, secure e-mailing with patients has not substantially impacted primary care provider workloads. Secure e-mail has been associated with increased member retention and improved quality of care. Separate studies associated patient portal and secure e-mail use with both decreased and increased use of other health care services, such as office visits, telephone encounters, emergency department visits, and hospitalizations. Directions for future research include more granular analysis of associations between patient-physician secure e-mail and health care utilization.