Steam-injection enhanced oil recovery began in California 40 years ago. Though several early pilot projects were steam-floods, most early applications were cyclic stimulation. During the late 1970s, steam-flooding became predominant. After the oil-price collapse in 1986, operators reviewed process fundamentals to determine how to operate steam projects more efficiently. The full-length paper discusses the shift to a gravity-drainage concept that led to reduced steam injection and unproved thermal efficiency through heat management.