Although human capital resources (HCR) can be important for organizational performance, researchers have defined and measured HCR in various ways. Consequently, it is unclear whether existing measures provide valid inferences about HCR or their relations with other constructs. We conducted this three-study research to address these issues. In Study 1, we reviewed HCR definitions (k = 84) and found that most definitions focus on collective knowledge, skills, and abilities. Recent definitions also tend to include other characteristics (e.g., personality). In Study 2, a content analysis of HCR measures (k = 127) revealed that only 23.6% of the measures focused solely on HCR and they tended to assess only one or two dimensions of the construct (i.e., were deficient). Many measures (46.5%) assessed both HCR and other constructs (i.e., were partially contaminated), and other measures (29.9%) assessed only non-HCR constructs (i.e., were fully contaminated). In Study 3 (k = 94), we found that HCR measures that were less deficient demonstrated stronger criterion-related validity for predicting unit and firm performance. Interestingly, partially contaminated measures were somewhat more predictive than uncontaminated measures (ρ =.35 vs..25, respectively), mainly because they assessed both HCR and other constructs that are related to performance. Both types of measures demonstrated stronger validity than fully contaminated measures. Overall, findings suggest that extant HCR measures often are deficient and/or contaminated. We discuss implications, as well as offer guidance for measuring HCR in future research.