The concept of molecular medicine dates back to Linus means that there are many new opportunities and challenges Pauling, who in the late 1940s and early 1950s generalized for clinical medicine. One of the effects of the completion of from the ideas that came from the study of the sickle cell the Human Genome Project is the increasing application of hemoglobin molecule. With the first cloning of human genes the fields of molecular biology and genetics to the und- about 1976, molecular genetics took the molecular perspec- standing and management of common diseases. Assimi- tive on disease to the level of DNA. The term molecular tion of the new developments since the first edition has been medicine achieved wide currency in the 1980s with the ably accomplished by Drs. Runge and Patterson with the assignment of this designation to journals, at least one soci- help of their many knowledgeable authors. ety, institutes, and academic divisions of departments of in- As was evident in the first edition, molecular genetics is ternal medicine. Undoubtedly, molecular medicine has been involved in every specialty of medicine. A recurrent theme abetted by the Human Genome Project, which has aided in that edition, perhaps even more striking in the present one, greatly in the molecular characterization of disease.