Objectives: To determine the reliability and validity of the ACT as a means to detect GINA-defined uncontrolled and partlycontrolled asthma (named as not-controlled asthma); and the agreement between ACT and GINA in classifying asthma control among Vietnamese asthmatic ambulatory patients aged 12 years or older. Methods: A cross-sectional study was done comparing ACT and GINA classification for asthma control among 323 asthmatic out-patients 12 years old or older seen at the University Medical Center in Hochiminh City, Vietnam.