One of the first researchers to specifically use the term 'outcome' in the context of health care was Donabedian, who defined health outcomes as 'a change in patients' current and future health status that can be attributed to antecedent health care' (Donabedian,1980). Until recently, methods adopted to assess quality of life as an outcome of health were described in non-specific terms, and reflect superficial understanding of this vital outcome. Fortunately, a great deal of advancement has been made in constructing instruments with emphasis on their accuracy as outcome measurement tools. This dissertation describes the work conducted to asses the psychometric performance and measurement properties (in terms of validity, reliability and responsiveness) of an asthma-specific outcome measure in New Zealand (the Asthma Quality of Life Questionnaire (AQLQ)). The validation process was conducted using pharmaceutical care provided by trained pharmacists as an intervention aiming at improving asthma outcomes, specifically the patients' quality of life.