Context - As men age, testosterone levels decline leading to symptoms that overlap with the symptoms of major depression. Little is known about the potential role of testosterone in the treatment of major depression.Objective - To assess the levels of bioavailable testosterone and total levels of testosterone in men diagnosed with major depressive disorder between the ages of 40 and 65.Design, Setting and Participants - 50 men between the ages of 40 and 65 and who suffer from major depressive disorder will be compared with 50 age matched healthy controls in an outpatient hospital setting. Main Outcome Measures - Bioavailable testosterone and total testosterone levels will be measured as well as blood pressure, pulse rate, height, weight, waist and hip measurements. Medical and psychiatric history will be assessed by the study physician. The Mini International Neuropsychiatric Interview (MINI) will be used to administered by the physician to ensure that the patient meets the DSM-IV criteria for Major Depression. The Hamilton Depression Rating Scale (HAM-D-17) will be used to assess depression symptom severity. A Symptom/Side Effect Rating Scale will also be administered to measure the presence and severity of side effects that each patient may be experiencing. In addition, the SEX FX questionnaire will be administered. Each patient will be asked to complete a series of self-report measures including the Social Adaptation Self-Evaluation Scale Questionnaire (SASS), the Androgen Deficiency in Aging Males (ADAM) and the Beck Depression Inventory (BDI-II).