This study examined the nature and correlates of adolescents' perceptions of sibling influence. Participants included 2 siblings (firstborn age M = 17.34; second-born age M = 14.76 years) from 191 maritally intact families. Adolescents' perceptions of sibling influence were measured via coded responses to open-ended questions about whether their sibling had an influence on them. Analyses revealed that older and younger siblings reported different patterns of influence. Differentiation influence and being a role model were more prevalent for firstborns, whereas modeling and modeling plus differentiation were more prevalent for second-borns. First- and second-borns' reports of influence were linked differentially to their relational and personal qualities. Discussion focuses on the need to refine the measurement of sibling influence processes. (Contains 2 tables and 1 figure.)