This study was designed to quantitatively assess the effects of short fiber (< 12.7 mm long) in raw cotton on the quality of 20s ring spun yarn. Twenty-eight bales of cotton with a wide range of fiber properties and an especially diverse population of short fiber content were utilized. Properties of the raw cotton were measured by High Volume Instrumentation (HVI), Advanced Fiber Information System (AFIS) instruments, and the manual Suter-Webb (SW) Array method. Ring spun yarns produced from these cottons were tested for process and product quality. Results indicate that most of the yarn properties—especially yarn strength, irregularity, and frequency of thick and thin defects—are strongly correlated with each of the three measures of short fiber content. A pool of 23 potential predictors from the AFIS, HVI, and SW fiber properties was utilized to develop "best" regression models for seven yarn properties. In five of the seven models, the short fiber content variable was the most important predictor, exceptions being the models for yarn strength and elongation. For five of the yarn properties, models developed using the four basic HVI properties alone were nearly as good in predicting yarn quality as those using all 23 fiber properties. Exceptions were models for elongation and for ends down.