OBJECTIVES:   Poor asthma control is associated with deleterious clinical and economic outcomes.  This research examined the association between asthma control and health-related quality of life (HRQL). METHODS: The Observational Study of Asthma Control and Outcomes (OSACO) was a prospective survey of asthma patients in Kaiser Colorado in 2011-2012.  Patients were mailed a survey three times in one year.  The survey included the Asthma Control Questionnaire (ACQ-6), mini-Asthma Quality of Life Questionnaire (AQLQ), EQ-5D and questions on asthma exacerbations and adherence.  A subset received spirometry testing and completed the ACQ-7 at National Jewish Health.  Regression analyses examined the impact of asthma control (ACQ) on EQ-5D, mini-AQLQ and VAS scores controlling for age, gender, family income level, race, educational attainment and ethnicity.  The functional relationship between asthma control and each outcome was estimated.  Different cut-points of the ACQ were explored (above-below .75, 1.0, 1.5; categories 0-1, 1-2, etc.; 0 - 0.75, 0.75-1.5, etc.). RESULTS: There were 2,683 respondents to the first survey of whom 596 completed spirometry.  The relationship between ACQ scores and HRQL was statistically significant and linear. Higher ACQ scores corresponded with lower HRQL for all instruments.  Each one-point increase in ACQ6 (ACQ7) score was associated with the following changes: -0.064 EQ-5D (-0.069 for ACQ7), -5.985 VAS (-4.5 for ACQ7) and -1.05 mini-AQLQ (-1.03 for ACQ7).  Different cut-points resulted in slightly different magnitude decrements but similar directionality for each HRQL instrument. CONCLUSIONS: Poor asthma control is highly correlated with decreased HRQL as measured by the mini-AQLQ and the EQ-5D.