The hospital's first appearance is at the beginning of Underworld, as Michael leaves his shift. Before heading home, Michael goes to the Intensive Care Unit, where the girl whose life he saved is recuperating from the gunshot wound she sustained in a recent subway shootout.
The next night, after Michael has fled from Ördögház, he returns to the hospital to get help for his wounds from Adam, but his explanation that he was bitten by a man does not convince Adam, who becomes worried about Michael's mental state and contacts the police, not knowing that the two police officers who have been looking for Michael are Lycans. Seeing the officers, Michael flees the building, eluding them for the time being.
- In the film, the hospital that Michael is interning at is called the "Saint Istvan Hospital". However, in the novelization, the hospital is called the "Károlyi hospital".
- There is a real hospital called "Károlyi Kórház", (Károlyi Hospital), in Budapest.
- According to the novelization, the hospital stocks plenty of Ziodex Industries products.
- The scene between Michael and Adam Lockwood in the hospital was the first scene to be filmed.