For more than a century now, Christianity's influence within many European countries has been in decline. Since especially the 1960s, there has been a corresponding and massive loss of church members. Despite the development of new forms of missionary engagement, the trend has not stopped, and it is very likely to continue for some time. What reasons lie behind it? How should the church address the challenges presented by this situation? These questions cannot, of course, be dealt with in detail in a single article. After the survey of statistical data and the range of its sociological interpretations, I will focus, third, on the missionary efforts conducted by the churches in Great Britain and Germany. Finally, I propose a specific missiology termed "oikumenical doxology" which I consider applicable to the situation in Germany, in particular, and European countries, in general.