Much remains to be learned about human genetics. Although it is likely that the entire human genome will be sequenced in our lifetime, full understanding of the regulation of gene expression and implications for gene therapy will take longer. The next phase of learning in genetics will certainly encompass these two areas of research. Much also remains to be learned about the implications of this knowledge on humans. Ability to achieve presymptomatic and prenatal diagnosis must be accompanied by an increased sense of responsibility for educating patients who receive these services and by exploration into the appropriate use of these powerful tools. It is essential for physicians to maintain a high level of sophistication about advances in human genetics, because when recombinant gene therapy becomes available, as it will, physician involvement will be critical to its ethical application.