It turns out that deuterium exists naturally. Of all of the hydrogen on earth, about .015% is deuterium. Since water is H2O, it follows that .015% of water is actually D2O. The slightly different properties of these two isotopes allow them to be distilled in a number of ways. Below is a link explaining a few methods of commercial interest.
http://www.ornl.gov/risk/t_section8.html
Created on Monday, March 12, 2001 11:04 AM EDT by Clay G Codner