This article considers the implications of the definitions and typologies of trance and shamanism for the development and testing of cross-cultural hypotheses through a review of definitions, typologies, and use of key terms and related concepts in anthropology. Authors vary widely in their definitions and applications of terms: some uses are based on reasoned criteria, others on traditional practice; some establish typologies, others prefer continua. Classifications range from narrow and highly specific to broad and inclusive coverage. Some restrict the usage to traditional societies, while others seek applications to Western phenomena, whether faith healers and mediums, or poets, such as Walt Whitman. The concept of control, with a variety of meanings assigned to it, emerges as a significant variable in the comparative study of“trance”and“shamanism”as these terms are used by different authors in widely different manners.