This study identifies social representations in interviews about alcohol and substance use in the discourse of 129 young adults, who were interviewed for 2.5 to 3.5 hr each for their life histories and use or nonuse of alcoholic beverages and drugs. Respondents spontaneously delineated their substance use boundaries, creating a continuum of behaviors with boundary points separating acceptable from unacceptable behaviors. They used signaling expressions to indicate go and stop signs and movement along the substance use continuum and reported negotiating substance use boundaries both internally and with peers. A ubiquitous narrative element was the cautionary tale, in which a negative exemplar goes too far with alcohol and/or drugs, providing an example of the possible negative outcomes of transgressing boundaries. In general, the narratives revealed complex relationships to alcohol and other drugs that may be useful in refining messages for more effective communication in prevention and intervention programs.