Significant unexplained and unintentional weight loss was found in 45 elderly patients who were identified by computer search of the diagnostic files of seven family practice centers. We performed a case series chart review study which revealed that 24% of the 45 cases had no definitive etiology for the weight loss after two years of extensive clinical investigation. Depression was found to be the most common diagnosis made (18%) followed by cancer (16%). Only four patients died during the study period and all had cancer. The most prevalent diagnosis in this group of ambulatory elderly patients did not prove to be cancer, as often though, but rather "unexplained weight loss." CT scans were not found to be helpful as screening tests in the evaluation of weight loss. Using the data from this study, the diagnostic evaluations of elderly patients with unexplained weight loss may be more efficiently directed.