This study presents an ethnographic account of the Mexican religious movement Espiritualismo Trinitario Mariano in the Mexicali/Calexico area, at the U.S.-Mexican border. A salient characteristic of espiritualismo is that its main practices, cátedras and curaciones, take place as spirit beings enter the bodies of trained individuals. In addition to providing a description of the main aspects of espiritualista ideology and practice, this study looks at the function of this religious movement in the border area in view of the following related factors: (1) the proximity of the United States; (2) the strong presence of Protestantism in the area; and (3) the infrastructural changes taking place in Mexicali, through industrialization and urban growth. Information was obtained through repeated participation in ceremonies carried out at temples, as well as through extended conversations with espiritualista participants and patients who attended the temples. Follow-up visits to homes of espiritualista practitioners were also made. In order to address the interests outlined above, two comparisons are made: first, between the practice of espiritualismo in Mexicali, at the Mexican side of the border, and the practice of espiritualismo in Calexico, at the U.S. side of the border; and second, second, between the practices of espiritualismo in Mexicali and those of espiritualismo in Mexico City, where the headquarters of the movement is located. The symbolic aspect of espiritualismo (including the particular personalities of the spirit beings that appear during practices) is thoroughly examined, as well as the particular socioeconomic conditions of participants in particular and temple attendees in general. Observations revealed that the particular characteristics of espiritualismo at the border reflect the awareness of its participants to attempts at discrediting tradition through the imposition of a "rational," hegemonic perspective. Through its practices and discourse, espiritualismo in Mexicali presents a front that challenges such impositions. Because of this, espiritualismo attracts not only the marginalized, as previously suggested, but individuals from all social levels in Mexicali and surrounding areas. In addition, an important finding is that the practices of espiritualismo, while striving to maintain tradition, they also help individuals to become attuned to the requirements established by globalization and modernity.