In 1800, who could have predicted that the theoretical basis of medicine would be transformed within a century by the demonstration that certain invisible organisms are capable of causing disease? Or, in 1900, that the theoretical basis of medicine would be transformed within a century by the demonstration of the genetic components of life processes? In 2100, what will be looked back upon that is unimaginable in January 2000?

As I plunge into the predictive waters, it would be no challenge to envision events so close to the shore that they will begin within the decade. So I'll start with two that are typical of innovations we can expect to see later in the century. The first deals with treatment and the second with diagnosis. Increasingly, pharmacologic therapies will be developed that are genetically specific not only to a class of diseases but to variations within patient populations and even individuals. In other words, the genetic contribution to many diseases will become so well understood that it will be possible to have drugs tailor-made for specific circumstances and patients.

The second easy prediction is of a continuation of the current progress in imaging which, when looked back upon at the end of the century, will seem like a veritable revolution. Scanning techniques will be so sophisticated that scarcely a physical or biochemical action within the body will escape surveillance. Diagnosis will be instantaneous, as exploratory surgery, biopsies and many blood tests become vestiges of a past that will appear archaic to the intern class of 2100.

Getting in just a bit deeper, I'll venture to say that this next century will be marked by a vast coming about in the attention focused on the role of science, and particularly biomedicine. Increasingly, priorities in research and application will be related to the concerns of the public; the relationship of scientists to the citizenry will be closer. Decisions about the direction of scientific endeavor will be made in light of the ethics, values and moral principles of the community that is to benefit, which will be an equal partner in those decisions. Laboratory research will not be as prolific and unrestrained as it is today, and public discussion will be far more informed. For this to take place, science education must be vastly improved, and this, too, will happen.

I don't believe that my final prediction puts me in danger of drowning. By the end of the 21st century--and probably long before--life, at least in the biological sense, will be created in the laboratory. The ability to synthesize short bits of DNA already exists, and it may lead to the creation of what is now being called a "minimal genome," which in the proper biochemical environment will be capable of ensuring metabolism and reproduction. It is not too early to begin thinking about this, and for public discussion to be heard, as it inevitably must be if we are to survive as an ethical society whose scientists and citizenry are united in a common effort directed toward human happiness.

Sherwin Nuland's latest book, "The Mysteries Within: A Surgeon Reflects on Medical Myths," will be published next month by Simon & Schuster.