To determine the relation of stressful life events to metabolic control.We interviewed adolescents with Type 1 diabetes (n = 132; average age at enrollment = 12 years) annually for 5 years.Each year we administered measures of stressful life events, psychological distress, and self-care behavior. We downloaded data from blood glucose meters, and obtained measures of metabolic control (hemoglobin A1c) from medical records.Using longitudinal growth curve modeling, stressful life events predicted greater psychological distress, poorer self-care behavior, and worse metabolic control in both cross-sectional and longitudinal (lagged) analyses. Cross-sectionally, many of these relations were stronger among older than younger adolescents. Self-care behavior partly mediated this association.Stressful life events are related to poor metabolic control-especially for older adolescents. A primary mechanism appears to be a lack of good self care. (PsycINFO Database Record (c) 2010 APA, all rights reserved).