Patterns of nonsuicidal self-injury (NSSI) and their association with other psychological difficulties were studied in a community sample of young Swedish adolescents, by a two-wave longitudinal design with a 1-year interval. Hierarchical cluster analysis at T1 identified eight NSSI subgroups in each gender, of which five were clearly replicated at T2. Among these were a subgroup with generalized high-frequency NSSI, which was associated with both internalizing and externalizing problems, and a subgroup of girls who engaged primarily in cutting and showed mainly internalizing problems. In general, NSSI clusters among girls were more stable over time and associated with more psychological problems. The results indicate that different patterns of NSSI have different developmental and clinical implications. (Contains 3 tables and 4 figures.)