Elderly patients hospitalized for management of major depression frequently have an extensive medical evaluation to determine if physical illness is masquerading as, or serving as the precipitating event for, the depression. The purpose of this study was to determine the incidence of newly discovered medical problems and the yield of various diagnostic modalities in such elderly depressed patients. Of 100 depressed geropsychiatric inpatients, the most frequent new diagnoses included: electrolyte abnormalities (6 patients), bacteriuria (13), medication reactions (7), exacerbation of previous thyroid disease (6), new thyroid function abnormalities (3), and renal failure, Parkinson's Disease, and chronic obstructive lung disease (2 each). One patient had a cerebellar hemangioblastoma, and 4 had acute illnesses. A workup including CBC, blood chemistries, urinalysis, and thyroid function tests frequently yielded abnormal results. When used as screening tests, head CT scanning, electroencephalography, and chest radiography did not affect management. We conclude that elderly depressed patients have a high prevalence of undiscovered physical illnesses, but that history, physical examination, and simple laboratory evaluation may be sufficient to guide their workups.