This study uses latent class analysis (LCA) to explore patterns of illegal behaviors (e.g., property and violent offenses), and substance use (e.g., alcohol, tobacco, or other drugs) among emerging adults (18 to 27 years). Data include 12,677 respondents from Wave 3 of the National Longitudinal Study of Adolescent Health (Add Health). Our study found that behaviors clustered into the following four classes: (a) the illegal and substance-use behaviors class (5.33%); (b) the fighting and substance-use class (5.24%); (c) the substance use class (28.30%); and (d) the normative class (61.12%). The analysis also incorporates indicator variables from Wave 1 onto the latent classes using the 3-step approach. Emerging adults most likely to be in the illegal and substance-use behaviors class with the highest prevalence of illegal behaviors were male; Black; younger; had histories of childhood physical abuse; or had friends at Wave 1 who drank, smoked, or used marijuana. Similarly, those most likely to be in the fighting and substance use class were male, Black, younger, reported childhood physical abuse, and had friends during Wave 1 who smoked or drank alcohol. Members of the fighting and substance-use class were also less educated than members of other classes. The substance use class was younger, less educated, less likely to be Black, had been physically abused, and had friends during Wave 1 who smoked or drank. Within the substance use class, no significant differences were found based on sex. We also found significant direct effects between peer influences and latent class indicators. Overall, results highlight the enduring influence of physical abuse and adolescent peer relationships.