http://www.commondreams.org/headlines05/0926-01.htm
The above article discusses the movie in more detail.
What I gather from it is a rather scary proposition. Here in the U.S. drug testing and other medical testing is highly regulated, and medical tests are routinely shut down when there are indications of problems. But outside the U.S. the standards are spotty or in some cases nonexistant.
The drug companies are toying with powerful chemicals. If they operate in the U.S. there's a lot of supervision which hopefully results in safer testing. But say there's a drug company that's chafing at U.S. regulations, and sees the opportunity to test their drugs outside the U.S. They would need to operate in countries having weak central governments and lax medical regulations. Fortunately for their purposes there are lots of poor countries that match those requirements.
That is the thesis of The Constant Gardener. The movie is said to be based on a true story, but of course fictionalized to some degree. They've probably tossed in some unnecessary car bombings or whatnot just because that's what movie directors do. But if the thrust of the plotline is anywhere near the truth, shouldn't we all be highly concerned?