OBJECTIVE To examine the relation between metabolic control and self-assessed quality of life in adolescents with IDDM. RESEARCH DESIGN AND METHODS The Diabetes Quality of Life (DQOL) questionnaire for youths was given to 69 subjects with IDDM aged 10-20 years at the time of their outpatient visit. Subjects with IDDM of < 1 year9s duration or with documented psychotic disorder or mental retardation were excluded. Metabolic control was assessed by the mean HbA1c during the preceding year (long-term), by a single HbA1c at the time of the visit (short-term), and by the number of acute events related to IDDM in the preceding year. RESULTS The DQOL score correlated with mean HbA1c (β = 6.13, R2 = 0.22, P = 0.0122) and single HbA1c (β = 3.94, R2 = 0.18, P = 0.05). Self-health assessment was the best predictor of DQOL score (β = −44.42, R2 = 0.45, P < 0.0001). The Worries subscale score on DQOL correlated with the occurrence of acute events (β = 6.97, R2 = 0.2, P = 0.006), but did not correlate with either HbA1c level. Correlations of mean HbA1c with the predictors were stronger than the correlations of single HbA1c with the same predictors. CONCLUSIONS Metabolic control and quality of life are two important outcomes of IDDM care. In our study, adolescents in better metabolic control report better quality of life. Both components need to be addressed in developing successful diabetes treatment strategies for adolescents with IDDM.