Religious experience played a prominent role in the psychological study of religion in the early decades of the twentieth-century, then waned as behaviorist and quantitative approaches became more prominent, and reemerged in the second half of the twentieth century alongside, and largely distinct from, mystical experience and, more recently, spirituality. Compared to the past, current research places less stress on sudden subjective experiences and more on ordinary (spiritual) experiences and gradual (spiritual) transformations that can take place in the context of practices or everyday life (struggle and coping). Ralph Hood, who is widely recognized as the leading expert in this area, makes a sharp distinction between religious and spiritual experiences, which must be defined by individuals and/or traditions, and mystical experience, which he views as a cross-culturally stable experiential core of religion and spirituality. Consideration of research on religious, mystical, anomalous, and pathological experiences, however, highlights considerable overlap between them and a lack of attention to the processes whereby they are differentiated within and across cultures. Researchers are developing new measures that separate experiences and appraisals, as well as new methods for ensuring that respondents understand queries in the way researchers intend. These innovations should allow us to better understand the effects of culture and tradition on the way unusual experiences are constituted in the context of everyday life.