This study tested Havighurst's (1948) contention that successful attainment of age-specific developmental tasks leads to happiness and success in achieving subsequent tasks. A longitudinal study on 146 participants was carried out to investigate the links between developmental progression in adolescence and young adulthood and happiness, which was assessed by two indices: high self-esteem and low symptomatology. The importance individuals place on achieving normative developmental tasks and current developmental status was assessed six times during adolescence and young adulthood, self-esteem and symptomatology were assessed five times. Results revealed a shift in the time frames for accomplishing the stage-specific developmental tasks. Findings with respect to the interrelatedness and progressive attainment partially supported Havighurst's contentions. Although remarkable concurrent links between the two indices of happiness and developmental status were found, developmental outcomes were not predictive for later happiness.