This paper is intended to summarize and correlate the results of the papers included in the two volumes that comprise the symposium on geologic structure held by the American Association of Petroleum Geologists. The examples of various types of structure that are cited are drawn largely but not entirely from the symposium. Although, on casual reading, many of the papers may seem to depart in some particulars from recognized structural principles, petroleum geologists are not misled by the seeming "exceptions" into supposing that conditions really conflict with the principles. Careful studies have proved that the accepted relationships of oil and structure prevail universally, subject to the control of other fundamental criteria. The advance of our science during the last ew years emphasizes the existence of many factors that were formerly unsuspected, any or all of which may affect the position of oil on, or in relation to, favorable structural areas. Every so-called "exception" is found to clinch the structural principles more firmly than before, and we can go forward with greater confidence despite seeming difficulties and can more keenly appreciate the pitfalls and the means for avoiding them.