According to one post, at http://www.drugs.com/forum/pill-identification/neo-percodan-21892.html
"Neo-Percodan is a mild narcotic pain med. It contains 500 mg acetaminophen and 65 mg propoxyphene. It's maybe a little stronger than Darvocet-N 50."
Having tried some myself, I found that probably to be true -- needed more of them to relive the pain than I would of Vicodin, but got none of the side effects (such as a high feeling).