Assessment of the clinical efficacy of diagnostic imaging technologies frequently involves reviews of published research. Reports may be classified in three dimensions; by disease, by type of assessment, and by the quality of research methods. The disease dimension describes the condition or conditions shown by an imaging technique. The assessment dimension spans five levels: technical capacity, diagnostic accuracy, diagnostic impacts, therapeutic impacts, and patient outcome impacts. The methods quality dimension can be expressed as four levels: excellent, good, fair or poor. An important interaction exists: the level of efficacy addressed by a research project dictates which methodologic procedures are important. For example, randomization is important only when a research report addresses the levels of therapeutic and patient outcome impacts. The authors suggest that classification of studies according to the three preceding dimensions maps the breadth (across diseases), depth (across levels of clinical efficacy), and quality of the assessment of complex imaging technologies. Such a map should help participants in technology assessment define the progress they have made. The classification strategy as applied to the clinical efficacy assessment of magnetic resonance imaging (MRI) for neuroradiology is illustrated.