Patients require good quality, evidence based information so that they can participate actively in the decision making process. The DISCERN instrument has been developed to help patients rate the quality of written information materials about treatment choices. This study evaluated the reliability of DISCERN using 31 information leaflets discussing treatment options for prostate cancer. The index of agreement between two independent raters was substantial for the overall quality rating (kappa=0.65, 95% confidence interval 0.49, 0.82), indicating that the instrument could be used to discriminate reliably between low and high quality prostate cancer publications. Healthcare professionals should inform patients of the availability of the instrument and encourage its use by patients who regularly attend to written sources of information on treatment choices. Early indications show that DISCERN could enable both patients and healthcare professionals to discriminate between the plethora of variable quality information currently available.