Summary The Crozat appliance is a precious-metal removable appliance which has been designed and developed to correct malocclusions and dentofacial deformities according to the concept and philosophy of Dr. George B. Crozat, for whom the appliance is named. The use of the appliance without full appreciation of that philosophy will bring failure and disappointment to him who employs it as a mechanism for straightening teeth. The appliance is not designed as a mechanical tooth-moving device. Rather, it is designed to deliver stress through the medium of the teeth to the supporting structures, resulting in tissue changes and, eventually, tooth movement. One must recognize to the fullest that in the correction of malocclusion we are dealing with an individual who continues to grow and develop from birth to maturity. Stress is applied to help this growth change from an undesirable form and shape (abnormal) to a desirable form and shape (normal) and, in so doing, to achieve a harmony of structure so that the results will become esthetically pleasing. It must be recognized that treatment cannot be a continuous process, beginning with a given deformity and proceeding through one or two school terms to a termination point when retainers are applied. It is, rather, a program of helping the patient grow and develop in the desired direction so that he may be brought up to par for his age and stage of development. In the Crozat philosophy, then, treatment does not suddenly end in retention, but treatment is gradually decreased or diminished as harmony is established—harmony in form and structure as well as harmony in function. In this connection, it should be thoroughly recognized that, with the changes taking place in growth and development, time is our greatest ally in bringing about a correction that will be stable. For him who is willing to study for an understanding and appreciation of growth and development, the Crozat appliance, used in harmony with the Crozat philosophy, offers a satisfying reward in orthodontic practice. In closing, may I say that the Crozat appliance, or any appliance, can be likened to a fine violin. It would be futile to hand a man a violin and a bow, tell him to play and make music, and then expect beautiful music to come forth. But teach him the theories of music and harmony, permit him to make simple beginnings with the violin, and in time, with practice and effort, beautiful music does come forth and the result is most pleasing and satisfying.