The names, social security numbers, phone numbers, addresses and patient care information of 42,000 patients were all on a laptop computer stolen from a nurse's home.
A spokesman for West Penn Allegheny Health System said they are not aware of any inappropriate use of patient information.
The computer and other possessions were stolen from a home care nurse's home.
The hospital said the data on the laptop is protected once the computer is shut off or when the battery runs out in about four hours.
Only home care and hospice patients could be impacted, not patients at the hospitals.
Patients are advised to put a fraud alert on their credit files and the hospital is offering a one-year free membership to a credit monitoring agency.
The computer was stolen Nov. 24, but patients weren't notified until letters went out on Dec. 15.
The data base on the laptop goes back to the year 2000.
Police have been notified and hospital officials are looking to add another safeguard to the laptops.