Dr. Catherine Eng is medical director of On Lok, a nonprofit organization founded in the early 1970s by a group of citizens concerned about the plight of frail elders and the lack of long-term options in the community. Eng has always had an interest in health care for the elderly. In 1981, she joined On Lok as a staff physician, and in 1992 became medical director of the health plan. On Lok SeniorHealth is a comprehensive health plan that provides long-term care for eligible seniors living in San Francisco and Fremont.