KKR, the private equity firm that reached a deal last month to acquire Raleigh contract research organization PRA International, is making another CRO buy and plans to merge the two companies into a single, global pharmaceutical services company.

New York-based KKR said Wednesday it has signed a definitive agreement to acquire ReSearch Pharmaceutical Services Inc, or RPS, from Warbug Pincus. As with the PRA acquisition, KKR is not disclosing how much it will paying to acquire RPS.

But KKR is giving some details of its plans. When both deals close, PRA and RPS will merge and PRA’s Chief Executive Officer Colin Shannon will lead the combined company. RPS will operate independently as the “Strategic Solutions Division” of PRA and it will continue to be led by RPS President Harris Koffer and Executive Vice President Samir Shah. But RPS CEO Dan Perlman will leaving RPS “to pursue other interests outside the CRO industry.”

“By bringing together PRA and RPS, we will be able to offer a more comprehensive range of services across all segments of the biopharmaceutical industry through our expanded capabilities, therapeutic expertise, and greater geographic presence,” Shannon said in a statement.

PRA had been considering an initial public offering of stock in a year that has seen a number of companies in the life sciences and health care sector go public, including Durham CRO Quintiles (NYSE:Q). Even though PRA had gone as far as filing the registration paperwork with the Securities and Exchange Commission private equity firms were said to be interested in acquiring the company. KKR emerged in late June as the buyer for the company. Although no purchase price was disclosed, Bloomberg News, citing an unidentified person familiar with the matter, reported the purchase price was $1.3 billion.

After the deal was announced, Shannon told WRAL TechWire that the acquisition by KKR would have no impact on PRA employees and in fact he expects KKR to grow the company. Wednesday’s announcement is indicates the kind of growth KKR has in mind.

Both PRA and RPS bill themselves as full-service CROs offering to pharmaceutical companies an array of services from early-stage to late stage clinical research. Of the two, PRA is the larger company. PRA has more than 5,300 employees and offers services in more than 80 countries.

Fort Washington, Pa.-based RPS was founded in 1998. The firm was more than 4,000 employees located in more than 64 countries. While the two companies may have overlapping locations, the merger does give the combined company the kind of global scale and breadth of services that the CRO industry’s biggest guns such as Quintiles and Covance (NYSE:CVD) offer. Analysts say that big CROs with global reach are most attractive to pharmaceuticals companies, who are increasingly reaching longer-term strategic partnerships with CROs. RPS was publicly-traded when Warburg Pincus announced in 2010 a deal to acquire the company for about $239 million in cash. The sale of RPS to KKR, subject to regulatory approvals and other customary closing conditions, is expected to close in the third quarter. KKR’s acquisition of PRA is also expected to close in the third quarter.

Citigroup acted as exclusive financial advisor and Kirkland & Ellis LLP acted as legal advisor to RPS. Credit Suisse, Jefferies LLC, and UBS Investment Bank served as financial advisors to KKR. Simpson Thacher & Bartlett LLP served as legal counsel to KKR. Fully committed debt financing will be provided by Credit Suisse, Jefferies, UBS Investment Bank, Citigroup, and KKR Capital Markets.