The question often arises of how health status is to be measured, or to what end. A number of instruments have been developed for the measurement of patient health, and the article consists in a review of the methodology and specific applications of some of those most commonly used, as outlined in published reports. The review showed the defined goal (s) of investigation to constitute a crucial determinant of the choice of methods, as most of the available instruments are designed for specific situations or categories of patients. Thus, an unfortunate choice may result in sufficient or erroneous data for the purposes of decision making.