The practice of psychoanalysis of neurotic conflict has not—to the extent that might be expected—evolved a consistent use in technique of available knowledge of the ego's mechanisms of defense. This is primarily related to a general resistance that can usefully be regarded as a "developmental lag." The evidence for this, particularly in Freud's writings, is reviewed as are the observations of others who have made note of this phenomenon. Some of the reasons that have contributed to this resistance among analysts are discussed.