Abstract: This study investigated the association of decision making autonomy with HIV/AIDS prevention knowledge among married women in Bangladesh. Data were used from the 1999-2000 Bangladesh Demographic and Health Survey (BDHS). For measuring women`s autonomy in decision making, we used six factors namely who take the final decision about: own health care; child health care; purchasing of large household materials; purchasing of household things for daily needs; visiting family, friends and relatives and what foods to be cooked. Using these factors, a combined score for autonomy was constructed using Likert method. Univariate analysis showed that 84% of women did not have any HIV/AIDS prevention knowledge. Multivariate logistic regression analysis revealed that women`s autonomy in decision making was an important correlate of HIV/AIDS prevention knowledge even after adjusting for some potential factors such as age, education, occupation, place of residence, exposed to radio, television and newspaper. Multivariate adjusted odds ratio revealed that women with highest score of autonomy had significantly higher knowledge of HIV/AIDS and prevention compared with women with no autonomy. Since Bangladesh is at risk for HIV/AIDS epidemic for several behavioral and biomedical risk factors, increasing women`s autonomy might be an important path to combat the consequences of HIV/AIDS in Bangladesh.