Background: Treatment compliance among patients with type 1 diabetes mellitus, is low in 50% of diabetic teenagers, becoming a social and medical problem. Aim: To determine psycho-social factors associated to treatment compliance among Chilean diabetic type 1 teenagers. Patients and methods: A non experimental study of 61 diabetic teenagers (age 14.9±1.9 years, 37 male). The number of blood glucose determinations, socioeconomic level and practice of sports was measured. Psychological tests were applied to analyze self-efficiency, motivation of achievement, self-esteem and knowledge of the illness and its treatment. As a measure of patient compliance, glycosilated hemoglobin (HB1Ac) was measured. Results: Six patients had a good control of diabetes (HB1Ac <7%), 24 had HB1Ac values between 7 and 8.9, and 31 (51%) had values of 9% or more, considered as a poor diabetes control. The intensified insulin treatment scheme, the knowledge of the illness and its treatment and the sense of self-efficiency, were the factors associated with a better compliance with treatment. Teenagers of higher socio-economical levels had a better compliance with treatment. Conclusions: Fifty percent of Chilean diabetic teenagers in this sample had a poor control of the disease and the variable knowledge about the disease is the better predictor of patient compliance (Rev Méd Chile 2005; 133: 307-13)