To describe the knowledge of HIV/AIDS among adolescents from different socioeconomic strata (SS), using cultural consensus analysis. A cross-sectional descriptive and analytic study was conducted from July 1995 to March 1996, among 758 adolescents from Guadalajara, México. Data were collected using a questionnaire, and analyzed by means of: a) consensus by SS and gender using factorial analysis; and b) identification of the cultural pattern of correct answers, and concordance of individual/group answers using Pearson's r correlation coefficients. There was a high degree of consensus across SS. The individual/group knowledge concordance was greater in higher SS. The pattern of correct responses showed: a) similar knowledge on casual transmission, AIDS characteristics, and higher risk in sex workers; and b) discrepancies regarding doubts and uncertainties about condom protection, distinction between HIV and AIDS, and HIV transmission in health clinics. Knowledge was homogeneous and mainly medically oriented across all SS. Nevertheless, there were elements of doubt and uncertainty that require differentiated informative interventions.