Within the domain of HR process research, one of the most prominent theories to explain how HR practices influence organizational performance is Bowen and Ostroff’s (2004) HR strength model. Based on the covariation principle of Kelley’s (1967; 1973) attribution theory, HR strength explains how three meta-features of an HRM system—distinctiveness, consistency and consensus—influence employees’ collective responses to the HR system. While Bowen and Ostroff construed HR strength as an organizational-level construct, it has mainly been studied as employee perceptions of the three meta-features. In this paper, we discuss three previous reviews of HR strength and examine the validity criteria of 41 empirical quantitative studies of HR strength. Theoretical implications are discussed in the last section of the paper.