This article reviews recent topics in health outcomes research. First, we discuss the concept and importance of 'subjective' assessment of quality of life (QOL), and introduce new guidance, by the respective medical product regulatory authorities in Europe and the United States, for labeling claims of medical products that are assessed for outcomes related to QOL. Second, we address the application of item response theory (IRT) in developing and assessing QOL measures to compensate for several drawbacks of the classical psychometric approach, which has been commonly used to verify the reliability and validity of QOL instruments. Third, the relevance and determination of the minimally clinically important difference (MID) of QOL scores is discussed. Finally, we address the so-called 'response shift' which may affect the reliability of analysis results of QOL scores in longitudinal studies such as randomized clinical trials.