Fil: Vacchino, Marta Noemí. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Epidemiología Dr. Juan H. Jara; Argentina.Fil: Velurtas, Susana María. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales; Argentina.Fil: Salinas, Guillermo Pablo. Laboratorio BAS; Argentina.Fil: Colino, María Cristina. ANLIS Dr.C.G.Malbrán. Instituto Nacional de Epidemiología Dr. Juan H. Jara; Argentina.Health effects of smoking have been studied intensely and there is substantial evidence on the harmful consequences for health that produces. In the last 20 years the effect of environmental tobacco smoke has been studied and researchers as governmentalagencies have concluded that involuntary smoking is one of the causes of lung cancer and cardiovascular illness in adults and of adverse consequences, like the syndrome of sudden death of the nursing, asthma, bronchitis and pneumonia in small children (1,2). Epidemiological questionnaires have been the usual method to determine exposition to environmental tobacco,but they present bias and low sensibility that can lead to misinterpretations of associations between exposition and illness (3,4). Cotinine, a metabolite from nicotine with a relatively short half life in plasma (about 20-30 hours), is useful as a biomarker for categorization and verification of a recent exposition (5). The goal of this work was to determine the level of exposition to environmentaltobacco smoke in a group of adolescents of the city of Mar del Plata, Argentina. (AU)