It appears from a review of the literature that at present a considerable number of psychiatric patients are being deprived of evidence-based treatment. However, Australian theoretical research has shown that if patients were to be treated entirely in accordance with evidence-based guidelines they would derive considerably more benefit from their treatment. This conclusion has been corroborated by various randomised controlled trials (RCT's) in which the effect of evidence-based treatment according to guidelines is compared with the effect of 'treatment as usual'. Studies carried out under less controlled circumstances than those prevailing in RCT's yield slightly less positive results. The literature stresses the difficulties of improving the quality of patient care. Studies on the implementations of guidelines show that carefully constructed, tailor-made interventions are needed to ensure that professionals adhere to guidelines. More research is required into effective ways of implementing guidelines in an adequate manner.