One hundred patients of lower socioeconomic class were intensively evaluated medically on a research ward for the presence of unrecognized medical illnesses that might have affected their hospitalization. Forty-six percent were thought to have medical illnesses that directly caused or greatly exacerbated their symptoms and were consequently responsible for their admission, while an additional 34% of patients were found to be suffering from a medical illness requiring treatment. A diagnostic battery of physical, psychiatric, and neurologic examinations, coupled with a 34-panel automated blood analysis, complete blood cell count, urinanalysis, ECG, and sleep-deprived EEG established the presence and nature of more than 90% of the illnesses detected, and is therefore recommended as an initial evaluation battery, particularly for patients facing involuntary commitment to a mental hospital.