This article describes the use of traditional Catholic beliefs and practices by Mexican sojourners in southeastern Pennsylvania to deal with and overcome substance abuse. Two practices in particular are the focus: juramentos and mandas. Juramentos are ritual promises to a saint, made by a drinker or drug user, to abstain from drinking or using drugs; whereas mandas are requests or pleas for divine intervention in protecting a loved one from dangers, including from substance abuse, made by the wives and mothers of the substance users. These religious practices were observed and studied while conducting alcohol and drug abuse research in southeastern Pennsylvania and teaching an ethnographic field school in Mexican sending communities to this region of the United States. Keywords: juramentos, mandas, immigrants, migrants, substance abuse, Mexico, southeastern Pennsylvania.