The growth of the shell-and-tube heat exchanger design has been a tedious task that has evolved over many years and will continue to mature for many more. Set forth in this paper are (1) a historical and chronological summary of the major contributions to the state of the art, with special emphasis on the contributions of Karl A. Gardner; (2) an analysis of the relationship of shell-and-tube heat exchanger mechanical design to the requirements of a process system; (3) a summary of some of the efforts presently being advanced; and (4) a challenge to explore and conquer areas in need of development.