Molecular biology is leading a revolution in our understanding, diagnosis, and treatment of disease and will continue to do so. Medicine in the future will require a greater understanding of this field and its methods by medical practitioners. This report reviews the basic aspects of the field including recombinant DNA methods. Of particular importance is how molecular biology will impact pediatric surgeons. Accordingly, the final section of this report briefly reviews the molecular biology of three diseases commonly treated by pediatric surgeons. J Pediatr Surg 34:917-939. Copyright (C) 1999 by W.B. Saunders Company.