Depression symptoms declined for both males and females from adolescence into young adulthood; however, females maintained more depressive symptoms than males throughout this period, even though males scored somewhat higher than females on the number and level of stress events during the study period. Stress was related to depressive symptoms for females but not for males, i.e., the number of stressful events experienced by male adolescents did not alter the course of their depressive symptoms. Females are apparently more susceptible to the adverse effects of stressful life events in terms of internal responses and their effects on mental health. A supportive relationship with parents was linked to a reduction in depressive symptoms for both genders. Although a mother's support was more effective in reducing depressive symptoms for females than father's support, father's support was not more effective for males than mother's support. In the latter part of the study period, support from either parent had no effect on depression trajectories for either gender. The National Longitudinal Study of Adolescent Health is a school-based survey of health and health-related behaviors of youth in grades 7 through 12. The sampling frame included all high schools in the United States. In the 1994 survey, a baseline sample of 20,745 adolescents was interviewed at home between April and December 1995 and between April and August 1996. They were reinterviewed between August 2001 and April 2002. Data for the current study came from multiple surveys administered over three waves of data collection. The surveys measured depressive symptoms, stressful life events, and parental social support. 4 tables, 1 figure, and 57 references