The Space Station Freedom (SSF) Thermal Control System (TCS) has evolved over a 12 year period in concert with a variety of configurations that have been proposed for SSF. The concepts for SSF have been influenced by the capabilities SSF will provide and by fiscal and schedule constraints. Changes in the capabilities the TCS must provide and the basic nature of the TCS design have been required to accommodate SSF needs and resources available.During 1991 the SSF configuration has reached a level of maturity and stability and details of the design are being worked. The design decisions that have lead to the present SSF and TCS design are described with the rationale that has contributed to the decisions. The TCS evolution through each of the design reviews (sometimes referred to as design “scrubs”) is presented to “capture” the major decision drivers that have contributed to the present TCS design.