-- -- tonight that some drugs Americans need for fighting serious disease could be counterfeit. In particular a vital cancer drug faked by counterfeiters overseas and -- -- tonight. That this... See More
-- -- tonight that some drugs Americans need for fighting serious disease could be counterfeit. In particular a vital cancer drug faked by counterfeiters overseas and -- -- tonight. That this discovery is just one revelation about a multi billion dollar industry of faking drugs. ABC's chief health and medical editor doctor Richard -- is on the case. -- -- is scared tonight with reason. It's. She's been on Avastin twice a month for four years. Like hundreds of thousands of Americans she counts on the lifesaving cancer current. -- she's frightened to learn today they clinics in three states California Texas and Illinois may have been giving patients a counterfeit version. A best -- isn't something you buy over the counter. It's dispensed intravenously by doctors and nurses to treat colon lung ovarian brain and kidney cancer. -- -- -- to paint no cancer fighting ingredient at all. The FDA found out from British authorities when label started falling off -- -- Avastin bottles over there. Take a look -- you -- -- the difference the box on the right the real Avastin only in English with the maker's name Genentech. On the left counterfeit and in French the -- Avastin was sold to the clinics from an unlicensed supplier. A supplier that -- in picking up the phone today we've seen cases like this before 200000. Bottles of fake Lipitor in 2003. And the Internet is a no man's land for counterfeit drugs from flu remedy Tamiflu to diet drug Ali. They need to know where they're getting their medicines and who they're getting their medicines from. Laura is counting on the FDA -- -- -- as much he's he's counting on Avastin to keeper colon cancer at day. Analysts Al Maroney and -- -- -- -- -- been so concerned. We're talking here about an unlicensed supplier. But if you're going online to an unknown web site to buy medications you really playing Russian let you have no idea where those are coming from. And who's watching over that supply and how much it could be happening and what do you say if you're someone wanted a vast and what you were getting and -- well I mean the good news if you call your doctor they can check your records and tell you immediately with -- -- -- the real drug.
This transcript has been automatically generated and may not be 100% accurate.