The aim of this study was to evaluate nocturnal and diurnal urinary melatonin excretion in a group of ischaemic stroke patients, and to verify if a possible impairment of this excretion could be linked with some changes of immunological and neuro-psychic status. We assessed 13 ischaemic stroke patients and five healthy controls for nocturnal urinary melatonin excretion, which was found to be impaired in stroke patients (patients, 0.05 +/- 0.01 ng/ml; controls, 30 +/- 3.0 ng/ml; P < 0.001). No differences were found between the groups with regard to diurnal excretion. Patients with impaired nocturnal melatonin excretion presented: a decreased cell-mediated immunity (assessed by a skin-test); a prevalence of anergic status (69% of patients were anergic compared with 0% of controls; P < 0.05); a slight (but not significant) enhancement of plasma cortisol levels; and some changes in lymphocyte subsets (an overall decrease in CD3 lymphocyte number). In almost all the ischaemic stroke patients there was an impairment of cortisol/melatonin ratio (a marker of depression) and an altered sleep rhythm with mood disorders. Our data suggest that ischaemic stroke patients had an impairment of nocturnal urinary melatonin excretion, which was associated with an impaired cell-mediated immunity and some changes of lymphocyte subsets. In addition, reduced melatonin excretion might be associated with neurological and psychical symptoms.