Rock music has during all of its almost 50 years of existence been the subject of criticism and debate. Much of this criticism has risen from religious circles. But also in these circles, rock music has its advocates. This thesis studies the reactions to rock music by spokespersons for institutional Christianity. Most of the material studied is written and published material. The material dates from 1983-1998 and originates from Sweden, Finland and the United States. The material is studied qualitatively. The purpose is to study the Christian discourse on rock music as an example of how institutional religion defends itself against competition. A theoretical perspective and conceptual apparatus is developed. The Christian discourse on rock is viewed as the defence of a monopolistic symbolic universe - institutional Christianity - against an outside threat - rock. This defence is described by two concepts, devaluation and incorporation. Devaluation involves giving rock an inferior status, for example defining it as demonic. Incorporation is an attempt to make rock part of the Christian symbolic universe. The result of devaluation and incorporation is the same: the denial of any reality outside the Christian symbolic universe. Several different techniques for devaluating and incorporating for example rock music can be used. Two such techniques are studied in the thesis: symbol interpretation, and the defence of boundaries. The main contribution of the thesis is the development and application of a theoretical perspective on how institutional religion defends itself against competition. The discussion on how established religion reacts to "secular" media adds an important dimension to the academic discussion on media, religion and culture.