"rb" wrote in message
news:cDAnh.19290$_X.3567@bigfe9...
We have some very dark spots randomly about our tongue-in-groove oak
flooring that were uncovered when we pulled carpets up. Friends tell me
it's probably from pet urine from previous owners.

I intend to refinish the floors and stay with bare floors. What is a
chemical treatment I can use to lighten those spots during refinishing?

Do what dpb told you. If it does not get it out to your satisfaction,
consider a stain on the wood to darken the rest of it so the spots don't
stand out as much.