We know from numerous industrial studies that stress, particularly in the form of tiredness and sleep deprivation, has a detrimental effect upon work performance, though this is not so clear-cut in studies of doctors, despite their stress levels being particularly high. This study explores the doctors' views on this using anonymous questionnaires from a population of 225 hospital doctors and general practitioners, 82 of whom reported recent incidents where they considered that symptoms of stress had negatively affected their patient care. The qualitative accounts they gave were coded for the attribution (type of stress symptom) made, and the effect it had. Half of these effects concerned lowered standards of care; 40% were the expression of irritability or anger; 7% were serious mistakes which still avoided directly leading to death; and two resulted in patient death. The attributions given for these were largely to do with tiredness (57%) and the pressure of overwork (28%), followed by depression or anxiety (8%), and the effects of alcohol (5%). The data are discussed in terms of the links made by the doctors between their fatigue or work pressure and the way they care for patients. It presumes that these incidents had been previously unreported and talks about the effects this secrecy has on the emotional state of the doctors concerned. It offers ways forward for tackling the problem, of interest to the profession, managers and commissioners.