Most theories of ritual are based on ethnographic descriptions of ritual actions around the globe. While many of these theories deal with performative aspects of rituals (the most famous being Tambiah [1981]) and wen more with the occurrence of possession within these rituals (see Boddy 19941, there are fewer accounts of rituals in which the central aspect is the participants' experience under the influence of psychoactive substances. This paper focuses on the representations of experiences during rituals and on the subjective theone$about these rituals by participants of the European Santo Daime church. My research is concerned with substance-induced altered states of consciousness and this paper attempts to link the insights of psychological knowledge about these substances with social theories on ritual. This appmach presupposes that an understandingof ritual, ritual action or ritual failure is only possible through the consideration of the participants' own understanding of it, especially as it is impossible to observe what is happening for the different participants during such a ritual as it all happens "in another world", namely in the consciousness of the participants.