ABSTRAC~ This paper demonstrates and compares methods for estimating the interrater reliability and interrater agreement of performance ratings. These methods can be used by applied researchers to investigate the quality of ratings gathered, for example, as criteria for a validity study, or as performance measures for selection or promotional purposes. While estimates of interrater reliability are frequently used for these purposes, indices of interrater agreement appear to be rarely reported for performance ratings. A recommended index of interrater agreement, the T index (Tinsley & Weiss, 1975), is compared to four methods of estimating interrater reliability (Pearson r, coefficient alpha, mean correlation between raters, and intraclass correlation). Subordinate and superior ratings of the performance of 100 managers were used in these analyses. The results indicated that, in general, interrater agreement and reliability among subordinates were fairly high. Interrater agreement between subordinates and superiors was moderately high; however, interrater reliability between these two rating sources was very low. The results demonstrate that interrater agreement and reliability are distinct indices and that both should be reported. Reasons are discussed as to why interrater reliability should not be reported alone.