What is the medical specialty of Gregory House's hospital department in House M.D.?

Gregory House's hospital department in House M.D. is Diagnostic Medicine.

The department investigates illnesses that other doctors have been unable to identify or treat successfully. House leads a small team of fellows, using differential diagnosis to compare possible explanations and eliminate them as evidence changes.

In real hospitals, diagnostic medicine is not always organized exactly as it is in the series. House M.D. dramatizes the work by giving one team responsibility for exceptionally rare cases and by compressing complex testing and consultations into television-sized stories.

The department's name also reflects the show's central idea: diagnosis is treated as an intellectual mystery. The characters must interpret symptoms, medical history, test results, and unexpected developments rather than simply apply a routine treatment.