PQRST is a first aid acronym taught in Red Cross Standard First Aid and First Responder to help the casualty describe his pain. This is generally done during the secondary survey. It stands for:
Provoked: What causes the pain? What makes it worse?
Quality: How does it feel specifically? Dull, sharp, moving, etc.
Region: Where is the pain located? Is it radiating elsewhere? (This is especially important for abdominal pain. A responder should be especially concerned if a casualty can pinpoint his abdominal pain to one area.)
Severity: How bad is it? (Responders generally use a scale from 1 - 10 where 10 is the worst pain the casualty has ever experienced.)
Time: When did it begin? How long has it been going on for?
Source: Canadian Red Cross, First Responder Manual: Second Edition.