The relationship between depression and chronic illness is reviewed with concentration on the latest research. The purpose of this doctoral project was to examine the prevalence of depression in patients with chronic illness, discover valid and reliable screening tools, explore potential risk factors for developing depression, and learn about proven effective treatment interventions. Quality of life is greatly effected by depression and co-occurring chronic physical illness because of the functional limitations that symptoms impose upon individuals. Depression can exacerbate inpatient hospitalizations, frequent doctor's office and emergency room visits, and individual efforts to self-manage chronic physical illnesses. It appears reasonable to assume that appropriate psychological interventions have the potential to reduce the number of visits to the emergency room, hospital, and/or doctor's office while increasing the individual's ability to provide self-care.