This article describes the National Park Service wilderness emergency medical services (EMS) system, as implemented at Sequoia-Kings Canyon National Park. EMS records on all 434 patients in the period from August 1, 1986, to July 31, 1987, were reviewed. Most patients had minor problems. Overall, 77% of patients contacting the EMS system were released at the scene, and base hospital contact was made in only 28% of cases. However, there were three deaths, 44 (10%) patients who received advanced life support, and 292 (67%) patients who received basic life support. Seven patients who received advanced life support were released without transport. Decisions regarding scope of practice in a low-volume, wilderness EMS system are complicated by long transport times and problems with skills maintenance. Differences between the times and problems with skills maintenance. Differences between the patients treated by a wilderness system and those seen in most urban systems may make it appropriate to release a greater portion of patients without ambulance transport. In a system with long response and transport times, use of personnel with different training than in the urban setting becomes necessary.