The validity of Hackman and Oldham's Job Characteristics Model was assessed by conducting a comprehensive review of nearly 200 relevant studies on the model as well as by applying meta-analytic procedures to a large portion of the data. The evidence indicated that the available correlational results are reasonably valid in light of the issues examined. Results tended to support the multidimensionality of job characteristics, but there was less agreement on the exact number of dimensions. The corrected correlational results of the meta-analysis indicated that job characteristics related both to psychological and behavioral outcomes. Concerning psychological states, the results tended to support their mediating (e.g., intervening) role between job characteristics and personal outcomes. The pattern of correlations between the job characteristics and psychological states was less supportive of the model. Meta-analytic results demonstrated that most of the cross-study variance was due to statistical artifacts. True variance across studies was found for the job characteristics-performance relationship, however, and subsequent analyses suggested that growth-need strength moderates this relationship. Implications for potential revisions of the model and for practice are discussed.