Evidence-based practice (EBP) involves complex and conscientious decision-making which is based not only on the available evidence but also on patient characteristics, situations, and preferences. It recognizes that care is individualized and ever changing and involves uncertainties and probabilities. Research evidence does not fall simply into "evidence-based" and "non-evidence-based" classes, but can be anywhere on a continuum from one to the other, depending on factors such as the way the study was designed and carried out. The existence of this continuum makes it necessary to think in terms of "levels of evidence", or categories of stronger or weaker evidence that a treatment is effective. Evaluation of research quality can be a difficult task requiring meticulous reading of research reports and background information. It may not be appropriate simply to accept the conclusion reported by the researchers. A number of protocols for the evaluation of research reports have been suggested and will be summarized here. Some of these divide research evidence dichotomously into EBP and non-EBP categories, while others employ multiple levels of evidence.