NEW YORK ( TheStreet) -- MSCI ( MXB) agreed to acquire RiskMetrics ( RISK), a risk advisory firm, in a cash-and-stock deal valued at about $1.55 billion. RiskMetrics' shares, under the terms of the deal, are valued at $21.75 a share. The stock closed Friday at $18.63, giving RiskMetrics shareholders almost a 17% premium. MSCI, known best for its MSCI international stock indexes, said its offer consists of $16.35 in cash and 0.1802 a share of MSCI for each share of RiskMetrics. The acquisition is seen closing in the third quarter. The transaction is expected to be financed by existing cash and debt proceeds. MSCI said it received a commitment letter from Morgan Stanley Senior Funding for senior secured credit facilities totaling up to $1.375 billion. The combined company would have about $750 million of revenue and about 2,000 workers across 20 countries. -- Reported by Joseph Woelfel in New York. Follow TheStreet.com on Twitter and become a fan on Facebook.