This study evaluated the impact of human resource (HR) management effectiveness and HR staff capabilities on firm performance. The researchers analyzed survey responses from 293 US firms across various industries. They found: 1) Firms achieved higher levels of technical HR management effectiveness than strategic effectiveness. 2) Both technical and strategic HR effectiveness were positively associated with measures of firm performance like productivity, cash flow, and market value. 3) HR staffs had higher levels of professional capabilities than business-related capabilities.