This guide covers emergency medical services from the obligation to treat through the bill and the liability claim. Part I explains the hospital emergency treatment obligation and what it does and does not require. Part II covers who operates ambulances and why that determines everything else. Part III covers coverage: medical necessity, destination, and level of service. Part IV covers billing, balance billing, and the federal framework that protects air but not ground transport. Part V covers air ambulance and aviation preemption. Part VI covers appeals and dispute resolution. Part VII covers EMS liability and immunities. Part VIII covers refusal, documentation, interfacility transport, and emerging models.