The spokesman for Ed Koch (KAHCH') says the former New York City mayor is improving but doesn't know when he'll be leaving the hospital.

The 88-year-old Koch was readmitted to NewYork-Presbyterian/Columbia hospital on Monday. He'd been released two days earlier after being treated for water in his lungs and legs.

Spokesman George Arzt says doctors on Tuesday continued to try to reduce the fluid. He says Koch also is showing an iron deficiency.

On Tuesday night, a new documentary about Koch's career premiered at the Museum of Modern Art.

Arzt says Koch asked about how many people attended, and who they were.

Koch initially went to the hospital on Jan. 19. He also was hospitalized in December with a respiratory infection and in September with anemia.