The purpose of this study was to develop a valid and reliable rating scale to assess jazz rhythm sections in the context of jazz big band performance. The research questions that guided this study included: (a) what central factors contribute to the assessment of a jazz rhythm section? (b) what items should be used to describe and assess a jazz rhythm section performance? (c) how should the items be categorized? (d) what differences among jazz rhythm sections exist at three performance achievement levels? and (e) what criteria best predict group membership into three performance achievement levels? Items were gathered from research and literature related to the assessment, teaching, and general discussions related to the jazz rhythm section. Twenty-nine item statements were paired with a four-point Likert scale. One hundred and twenty-two responses were gathered from 41 volunteer raters. The results of the data were factor analyzed and yielded a two-factor structure including rhythmic support/drive and style/clarity. The 16-item scale accounted for 79.23% of the variance and the alpha reliability was estimated at 0.986. The rhythmic support/drive factor contributed most to discriminating between overall group differences. More specifically, five out of the 16 items contributed most to discriminating between groups.