Science is making progress in understanding how cholesterol damages human health, and the pharmaceutical industry is tackling the challenge with a variety of drugs, says Fred Hassan, chairman and chief executive of Schering-Plough.

The company is completing the purchase of Organon BioSciences to gain access to medicines in that company’s research pipeline like asenapine for schizophrenia. It reports first-quarter earnings on Thursday. Following are excerpts from a recent conversation:

Q. Why do Americans have such a huge problem with cholesterol?

A. The problem has become more visible because science is now validating what was seen in the Framingham study that followed many people in the town of Framingham, Mass., for decades. They came up with this hypothesis: if you have high levels of L.D.L.’s [low-density lipoproteins], you have a problem. If you can reduce the L.D.L. part, the bad cholesterol, you have a much better outlook when it comes to heart attacks and strokes.

Q. Has our rich lifestyle contributed to the problem?

A. It’s partly heredity, partly lifestyle. They’ve done studies in some countries where people are pretty lean, but had cholesterol problems, like the farmers in Finland. The studies say that in China 30 or 40 years ago, before things got mechanized, people had much lower L.D.L.’s than they do now.

Q. Do all the additives in our foods have an impact on our cholesterol?

A. Yes, if you eat too much of the bad stuff, especially these hydrogenated fats, the margarine-type things, that’s not good. And also there’s now a growing theory, if you are obese because of eating too many carbohydrates, that doesn’t help you. It’s a whole bundle of problems.

Q. How does your drug Zetia attack the cholesterol problem?

A. Cholesterol, including L.D.L.’s, are manufactured in the liver. Statins, which came into the market in 1987, work by interfering with that process in the liver. But Zetia, which was a major advance we achieved in 2002, prevents the absorption of bad cholesterol in the gastrointestinal tract. It’s a separate mode of action. That’s helpful for a whole bunch of people who don’t tolerate statins very well.

Q. Is that fundamentally different from what Pfizer’s Lipitor does?

A. Yes. Lipitor works in the liver. And we work more in the gut. Vytorin works for both. That’s a drug we share with Merck in a joint venture.

Q. What drugs did you recently acquire?

A. We have five projects in Phase 3 of clinical trials. That means you’re not far from registering and launching the drug. The one that gets written about the most is called asenapine, which is for schizophrenia and bipolar disorders. There is a huge demand for new drugs in this area because many existing drugs don’t work. Patients sometimes have to cycle through different drugs before they find the right one. And some of them have controversial side effects such as obesity.

Q. Is Schering-Plough unusual in having this many new drugs or is the whole industry on the verge of delivering new compounds?

A. We as a company are doing better than we’ve ever done in our history. I just met with our researchers, which is not very usual for a C.E.O. But I see research as the primary engine.

The industry as a whole is going through a tough time. There is a lot of concern over safety. When that happens, the balance moves in favor of asking more questions and more studies. The cost of developing new drugs has gone up. It has created an economic imbalance for some companies. That’s why you see a lot of people reductions and layoffs at companies where their ability to come up with new drugs is not keeping up with the rate at which drugs are going off patent.

Q. Wouldn’t you agree that the image of the pharmaceutical industry has taken a hit because of pricing?

A. We as an industry have worked very hard to reduce the pain by working with the government on reimbursement and trying to have patient assistance programs for those who have issues making co-payments. By and large, a lot of the burden has been lifted from the seniors who are a very large part of the market. But we have to do a lot more for the uninsured and the underinsured. And we have to be honest with each other and understand that if we are looking for better-quality care and longer lives, we have to make more money available for health.