Designs of physically large and complex (PL&C) systems, nowadays, are achieved through the use of evermore capable digital computer-based techniques. Thus, the process of such designs might be characterized as the practice of science rather than that of an art. The article commences with a consideration of art and science in design. It then addresses the particular nature of the design of such systems and how this is not just an issue of complexity, but also a consequence of large physical size. How computer-aided design is applied early in the designing of such systems, the crucial aspect of the choice of style by the initial designer and the advent of computer-based simulation techniques, applied early in design, are all considered pertinent to the role of art and science in design. A series of high-level fundamental issues are discussed in the belief that they are changing the nature of the design of PL&C systems and ought to be considered by practitioners of such designs. In this way, the power of computer-based techniques, both numerical and graphical, can then enhance the scope of design innovation, given designers' increasing dependency on digitally based practice.Keywords: design of physically large and complex systems; art and science; design building block approach