The chief executive officer of the California Public Employees’ Retirement System is resigning, marking the second top official at the nation’s largest pension fund in under a week to announce plans to quit, the Wall Street Journal reports.

Fred Buenrostro said in an interview late Monday, “I’ve passed up opportunities in the private sector before but the timing is good now. I put a succession plan in place.” The timing of his departure wasn’t clear, but he said he expected to leave by year end.

Mr. Buenrostro, 58 years old, has been CEO since 2002 and served on the Calpers board for several years before that. The $244 billion California pension fund provides retirement and health-care benefits for about 1.5 million public employees. The fund returned about 19% for the fiscal year ended June 2007.

The announcement comes just days after Russell Read, chief investment officer of Calpers, revealed plans to resign in June after two years at Calpers to pursue his interest in environmental investing. In February, Christianna Wood, who as a senior investment officer oversaw $150 billion of stock investments, left to work for a New York firm that invests in hedge funds.

The unusual number of high-level personnel moves comes at a time of transition for Calpers, and could leave the giant pension fund without some top leaders just as it is moving into new investments. Calpers recently increased the fund’s exposure to foreign stocks, and began investing in Asian real estate and directly in commodities. The fund also took stakes in some private-equity firms, including a 10% stake in Silver Lake Partners earlier this year. Under Mr. Read, it initiated a program that will focus on infrastructure investments in areas such as shipping, transportation, and production of fuels and electricity.

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