In recent years various studies of a religio-sociological nature have supplied numerous data relating to the catholic and protestant diaspora. These data have not yet been integrated in general sociological systems. Influenced especially by German organisations which have concerned themselves with the dispora since the last century, a specific knowledge of the diaspora has been evolving, but this is dominated by the theological element. For the interest in protestant circles see the periodical "Die Evangelische Diaspora" appearing since 1919, and the chair established at Leipzig University in 1934 to study diaspora problems. On the catholic side there may be mentioned the Johann Adam Möhler Institut für Konfessions- und Diasporakunde, at Paderborn, which collaborates closely with the St. Bonifatiusverein. The Catholic Institute for Social-Ecclesiastical Research in the Netherlands and the Catholic Centre for Social Research at Königstein/Ts, Germany, have made various religiographic studies in recent years on the catholic diaspora in the Netherlands, Germany and Scandinavia. In the U.S.A., important works have appeared on relations between catholics and protestants (among others by Will Herberg, J. Kane et al.), which show interesting analogies with European studies. Reviewing progress of the still fairly heterogenous socio-scientific study of diaspora phenomena, the question is raised of the possibility of integrating the facts described in a theoretical system. The theoretical work by R. K. Merton, regarding his system of functional analysis, can be examined to see if it can serve as a theoretical framework for studying the diaspora. As regards Merton's question of observability reference is made to the special difficulty in this respect inherent in the diaspora. Although, sociologically, the study can be confined to parishioners known as such, the question arises whether the diaspora with its geographically widespread parishes does not especially require non-parochially integrated baptised catholics to be included theoretically in the diaspora structure. In the Province of Friesland in the Netherlands, in parishes with 300-800 parishioners there were found to be 100 or more baptised not parochially registered. A complicated question, too, is that of the existence and meaning of personal attitudes to the diaspora. The dilemma is given between social absorption in the over-all environment and the creation of an individual environment. For the forming of the faithful in the diaspora the choice will depend largely upon the value attributable to the religious content of the over-all environment. It would also seem to be profitable to apply the concepts "functional" and "dysfunctional" to the diaspora. Positive functions rest in the Churches' Oecumenical consciousness. In the individual Church the diaspora may act as the territory pre-eminently suitable for pastoral experiments and for activating help to fellow-believers. But the diaspora may also have a dysfunctional effect relatively to the Oecumenical idea: for considerations of security the position of the majority church may be painted too darkly. Besides, isolation may be so great that the approach is sought solely for the sake of approach without sufficient care to the fundamental theological aspects. For analysis of the diaspora phenomenon, Merton's concept of functional requirements is also profitable. The diaspora demands special intensification of contacts, particularly with the "other Christians", puts great emphasis upon moulding of the personality and of the group. Important, too, are special organisational arrangements in the light of the social mechanisms indicated by Merton. One may recall in this connection the recent formation of the diaspora diocese of Groningen in the Netherlands. The extent of the diaspora parishes also calls forth the question of establishing auxiliary churches. The family becomes especially important to religious training (catechism), and so does a weekly periodical where the extent of the group precludes their having their own daily paper. Finally, attention is drawn to the limits of action of the diaspora system: these limits form the structural context. Possibilities in the diaspora are limited as regards facilities for education, medical care, cultural contact, etc. Economic factors may encourage mixed marriages to an exceptional degree in the diaspora. Positive action by the clergy is possible in all these respects only with the assistance of bodies and organisations outside the diaspora. The application of functional analysis can be expected to deepen insight into the phenomena of the diaspora and to help to make investigation of the very complicated diaspora situations in Northern Europe, both catholic and protestant, more effective for the study of the pastoral methods required in varied ways in the diaspora. [ABSTRACT FROM AUTHOR]