This longitudinal study examined change in adolescents' daily range of emotional states between early and late adolescence. A sample of 220 youth provided reports on their daily emotions at random times during two 1-week periods. At Time 1 they were in the fifth through eighth grades; 4 years later, at Time 2, they were in the ninth through twelfth grades. Results showed that average emotional states became less positive across early adolescence, but that this downward change in average emotions ceased in grade 10. The results also showed greatest relative instability between youth in the early adolescent years--correlations over time were lower--with stability increasing in late adolescence. Lastly, the study found that adolescents' average emotions had relatively stable relations to life stress and psychological adjustment between early and late adolescence. As a whole, the findings suggest that late adolescence is associated with a slowing of the emotional changes of early adolescence.