A new Consumer Reports study ranks Harlem Hospital the worst in New York City and the second worst in the entire country.
Consumer Reports said patients suffering from pneumonia and heart ailments were readmitted too often within 30 days of the diagnosis.
Brooklyn's Kings County was ranked second worst.
Consumer Reports also cited both hospitals for having too many patients infected by catheters and during surgery.
NYU Langone received the best score in the city.
Peninsula Hospital Center in Queens was ranked second best, despite the fact that it closed in April.
But the city's Health and Hospitals Corporation, which runs public hospitals, took issue with the study.
"Using outdated data and flawed methodology, this report fails to represent an accurate picture of the excellent patient care and significant improvements achieved by these hospitals.," an HHC spokesperson said in a statement.