Do root canals hurt during and after the procedure?

Rarely: With good anesthesia, root canal therapy rarely hurts during the procedure. Sometimes if a person is really hurting before the procedure is started, good anesthesia isn't always possible. I hear of pain afterwards, a very small percent of the time.

No and maybe: Typically a root canal shouldn't hurt during the procedure. If the tooth is extremely infected or "hot" it can hurt only until the endodontist gets to the nerve space, at which point they can get the anesthesia directly at the cause of the pain, and have a painless procedure after. As farad after the root canal, the level of pain is relative to the pain you had coming in.