Massachusetts Pension Reserves Investment Management Board, Boston, portfolios returned a total of 23.18% in calender 1999, said Scott Henderson, executive director for the $30.7 billion fund. Separately, the systems trustees approved up to $215 million in new private equity commitments. The system approved up to $75 million to GTCR Fund VII and up to $75 million to Texas Pacific Group III for buyouts; and up to $50 million in J.H. Whitney Fund IV and up to $15 million in Polaris Venture Partners III for venture cap. Funding will come from domestic equity and fixed-income allocations, Mr. Henderson said. PRIM also approved a target allocation of $825 million for new opportunities in alternatives, excluding real estate, in 2000.