We aimed to assess the role of spiritual belief in clinical outcome of patients nine months after hospital admission. Two hundred and fifty patients admitted to a London teaching hospital were recruited and followed up for nine months. Outcome measures were clinical status as recorded in the outpatient records and patients' self reported health status and beliefs. A hundred and ninety-seven (79%) patients professed some form of spiritual belief, whether or not they engaged in a religious activity. Strength of belief was lower in patients who were in a more serious clinical state on admission (F = 3.099, d.f. = 2 and 192, p = 0.05). Case note information was available nine months later for 234 patients (94%) and contained useful information for judging clinical outcome in 189 (76%). Patients with stronger spiritual beliefs were 2.3 times more likely (CI = 1.1-5.1, p 0.033) to remain the same or deteriorate clinically nine months later. Other predictors of poor outcome were male gender and sleep disturbance at time of admission to hospital. We conclude that a stronger spiritual belief is an independent predictor of poor outcome at nine months in patients admitted to two acute services of a London hospital. It is more predictive of outcome than physical state assessed by clinicians, or self-reported psychological state, at admission.