Demonic possession among Roman Catholics in Sri Lanka has increased rapidly in recent years. This paper is concerned with analyzing demonic possession from the point of view of its existence as a collective representation. It is argued that the collective representations of possession precede the actual incidence of possession and that any analysis of possession must start from the collective representations rather than from the incidence or the individual experience of possession. Demonic possession is shown to be a form of rite de passage, closely related to life-cycle rituals and to concepts of illness. Finally, it is shown that the actual incidence of possession is defined by the collective representations of demonic possession.