Recently, there has been a remarkable upsurge in activity surrounding the adoption of Personal Health Records (PHRs). Since PHRs contain global patient information and not certain pieces collected by individual healthcare providers, they can be used as basic infrastructures for building and operating several important systems for both healthcare and the tax payers. Emergency medical systems (EMS) are among the most crucial ones as they involve a variety of activities which are performed from the time of a call to an ambulance service till the time of patient's discharge from the emergency department of a hospital and are closely interrelated so that collaboration and coordination becomes a vital issue for patients and for emergency healthcare service performance. This paper is concerned with the development of a PHR-based EMS in a cloud computing environment. Cloud-based services can prove important in emergency care delivery since they can enable easy and immediate access to patient data from anywhere and via almost any device.