PURPOSE A Web-based consultation system (telenephrology) enables family physicians to consult a nephrologist about a patient with chronic kidney disease. Relevant data are exported from the patient's electronic file to a protected digital environment from which advice can be formulated by the nephrologist. The primary purpose of this study was to assess the potential of telenephrology to reduce in-person referrals. METHODS In an observational, prospective study, we analyzed telenephrology consultations by 28 family practices and 5 nephrology departments in the Netherlands between May 2009 and August 2011. The primary outcome was the potential reduction of in-person referrals, measured as the difference between the number of intended referrals as stated by the family physician and the number of referrals requested by the nephrologist. The secondary outcome was the usability of the system, expressed as time invested, the implementation in daily work hours, and the response time. Furthermore, we evaluated the questions asked. RESULTS One hundred twenty-two new consultations were included in the study. In the absence of telenephrology, 43 patients (35.3%) would have been referred by their family physicians, whereas the nephrologist considered referral necessary in only 17 patients (13.9%) (P <.001). The family physician would have treated 79 patients in primary care. The nephrologist deemed referral necessary for 10 of these patients. Time investment per consultation amounted to less than 10 minutes. Consultations were mainly performed during office hours. Response time was 1.6 days (95% CI, 1.2-1.9 days). Most questions concerned estimated glomerular filtration rate, proteinuria, and blood pressure. CONCLUSION A Web-based consultation system might reduce the number of referrals and is usable. Telenephrology may contribute to an effective use of health facilities by allowing patients to be treated in primary care with remote support by a nephrologist.