Tenet Healthcare Corp. and Catholic Healthcare West have been at the forefront of a consolidation movement that has swept up dozens of hospitals in L.A. County. Here is a rundown on the county’s three biggest hospital chains.

Tenet Healthcare Corp.

Headquarters: Santa Barbara

No. of Hospitals in L.A. County: 16

Industry giant Tenet, the second-largest private health care system in the country, became the largest operator of Los Angeles County hospitals early last year when it bought OrNda HealthCorp and its 10 facilities. Tenet now owns 16 hospitals in the county, including its most recent acquisition, the 101-bed Queen of Angels-Hollywood Presbyterian hospital.

The sale was a controversial one, but Tenet is no stranger to controversy. Its predecessor, National Medical Enterprises, faced a host of allegations of civil and criminal wrongdoing and paid more than $370 million in fines. Last year, the company agreed to pay about $100 million to settle charges of false imprisonment of psychiatric patients, and also agreed to pay another $12.6 million to settle allegations of wrongdoing by OrNda.

The company, which changed its name in 1995, has said those previous problems occurred in subsidiaries it no longer owns, and that safeguards have been put into place to make sure they won’t reoccur.

For its first quarter ended Sept. 30, the company reported net income of $136.6 million, compared to $116.2 million for the like period a year ago.

Catholic Healthcare West

Headquarters: San Francisco

No. of Hospitals in L.A. County: 9

Catholic Healthcare West, the state’s largest non-profit health system, will own nine hospitals in the county after it completes its merger with UniHealth at the end of the month.

The company traces its history back more than 100 years when the Sisters of Mercy religious order opened St. Mary’s Hospital in San Francisco. Since then, numerous California religious orders that operated hospitals joined forces to form Catholic Healthcare West. The new company anticipates having more than 13,000 employees, and 2,300 doctors on its active medical staff.

The company’s policy, pursuant to Roman Catholic doctrine, of not allowing abortions at its facilities has sparked some controversy.

Kaiser Permanente

Headquarters: Oakland

No. of Hospitals in L.A. County: 7

Kaiser Permanente Group, one of the nation’s oldest HMOs and the largest in the country, differs from other health care companies in that its system is self-contained: the HMO owns and operates its own hospitals. Thus, it has concentrated its expansion efforts not on acquiring hospitals, but on enlarging its subscriber base by offering cheaper rates than other HMOs.

Last month, the company reported that its third-quarter losses from operations totaled $111 million, bringing year-to-date operational losses to $240 million. Losses for the whole year will probably be about $270 million, roughly similar to last year.