Santa Barbara Research Center, Hughes, and Hughes Technology Center have designed and built second generation readout circuits since the early 70's. This paper will discuss the evolution, problem areas, and system design drivers that drove the development of these circuits. The discussion will range from the earliest monolithic implementation of the readouts to the newer hybrid approaches which incorporate a high level of integration. Areas addressed will be the transition from NMOS or PMOS to CMOS, development of design rule's technology, yields, costs, and performance. All these topics will show how these developments affected readouts and second generation infrared sensors. We shall also speculate on the future developments in ROIC technology.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.