The production of clinical guidelines has become an accepted and lauded part of modern medicine. It is also widely perceived that these guidelines provide some sort of panacea for the problems that medicine faces. Our experience suggests otherwise. Triggered by on going anecdotal evidence of poor practice, we reviewed the effect on practice of a recently introduced local guideline on the management of major bleeding in patients on warfarin. Comparing 34 patients treated before and 48 patients after the introduction of the guideline, we found no significant improvement in prothrombin complex concentrate dosing or administration of vitamin K. The only improvement witnessed was in early assessment of the effect of the intervention on coagulation which improved from 10 to 35% of cases. Of major concern, in 10% of cases, there was no documentation to confirm or refute that prothrombin complex concentrate (PCC), which had been issued, had actually been administered to the patient. The production and widespread dissemination of this local guideline did not achieve significant improvement in clinical practice. Possible reasons for failure to adhere to the guideline are discussed.