System One, which ranks on SIA’s list of largest US staffing firms, acquired GAP Solutions Inc., a professional services firm providing staffing and services to US government organizations.

The transaction closed Dec. 4; terms were not disclosed.

GAP Solutions’ services include human capital management, security process management, scientific and technical expertise, and operations management.

Headquartered in Herndon, Va., GAP Solutions will keep its existing brand and operate as a System One company. GAP Solutions’ President Diane Pairel and its operational leadership will remain.

“We are excited to bring GAP Solutions, Inc. into the System One family,” said Troy Gregory, president and CEO of System One. “The expertise and reputation of GAP Solutions’ team aligns with our strategy of providing mission critical services, broadens our reach in the federal market, and creates opportunity for our continued growth.”

System One ranks No. 22 on SIA’s list of largest US staffing firms. It’s based in Pittsburgh, and its top segments served are engineering and IT.