D and L stereoisomers

pzona

I was wondering about this earlier today: how do they (IUPAC?) decide which stereoisomer is D and which is L? I understand the difference between the two, but I don't know how to determine which is which. I imagine it has something to do with chiral priority, but could someone explain, or give me a resource on this?

Borek

http://en.wikipedia.org/wiki/Chirali...ng_conventions