Emergency medical services are provided by rangers on duty. Call 911 in case of an emergency.

Medcor operates three urgent-care services within the park. The clinic at Mammoth is open year-round, staffed by a board-certified physician and a team of experienced RNs. The clinics at Lake and Old Faithful are open seasonally (see below for schedules).

All of these clinics are open to the public and are staffed and equipped for most medical emergencies as well as for routine care. Servcies include injury and illness treatment, x-rays, and some lab and pharmacy services.

If in-patient care or advanced services are required, the clinic staff can stablize patients and arrange for appropriate transfer to a hospital outside the park.