Suicide is one of the leading causes of death in the community. The risk of suicide is greater among patients with physical illnesses than among the general population. This study was undertaken to evaluate the clinical characteristics and correlates of suicidal ideation in patients with acute life-threatening physical illnesses and to assess the duration of suicidal ideation. The study included a consecutive series of patients admitted with stroke, traumatic brain injury, myocardial infarction, or spinal cord injury (n=496). Study participants were administered a semistructured psychiatric interview as well as a series of standardized quantitative scales of mood, cognitive function, physical impairment, social ties, and social functioning. Follow-up evaluations of up to 24 months were also carried out. This study found that 36 (7.3%) patients with acute medical illness had clinically significant suicidal ideation. The suicidal ideation occurred mostly among patients with major depression and sometimes in those with minor depression. About 25% of patients with major depression and acute physical illnesses developed suicidal ideation. After the improvement of depressive disorders, suicidal ideations were ameliorated. These findings suggest that the detection and treatment of depressive disorders is the most important factor in preventing suicide among this patient population.