Many of us believe there are major benefits to be gained by using patient-reported outcomes (PROs) in routine clinical practice. However, demonstrating tangible benefits has frequently proved elusive. Although randomised clinical trials (RCTs) have become accepted as the standard for comparing alternative forms of clinical interventions, when evaluating the effectiveness of PROs there are a number of challenges both in terms of study design and the subsequent analysis. Despite this, to date, of those investigators who have used RCTs, relatively few have used anything other than simple two-group randomisation and comparisons. Most of these trials have also failed to demonstrate convincing benefits to patient outcomes. We suggest that the use of PROs may result in modest yet important improvements to patient outcomes, and that these benefits may be obscured in conventional individual patient trials because of contamination effects. The advantages of alternative designs such as cross-over studies and in particular cluster-randomised trials are illustrated.