Sexing Rats: RatRaisins.com
RatRaisins has several pages on sexing rats. If you roam the RatRaisins site and want to return to the page below on the links in the RatRaisins Sexing section, here is the direct link: http://www.ratballs.com/RatTails/_sexing.html.
Careful: Separate baby boy and girl rats from each other, and the boys from their mother, by age 5 weeks, or the females will become pregnant and you'll start all over again!
Now for some more wisdom from Rat Raisins. If you roam Rat Raisins, and want to return to the pages below, they are: