The effect of the short fiber content of a cotton on yarn and fabric properties and processing efficiency, long a speculative and controversial subject, is investigated to a limited extent in this paper by the technique of cutting sliver into and ¼- and ½-in. segments and adding the resulting short fibers to the parent cotton. The results indicate that increases in short fibers are detrimental to virtually all yarn and fabric properties and require increased roving twist for efficient drafting during spinning. A 1% increase in fibers shorter than 3/8 in. causes a strength loss in yarns of somewhat more than 1%. The quantities of cotton processed for this paper were insufficient to draw conclusions on neps, waste, or processing efficiency. The effect of short fibers on these properties will be considered in subsequent papers.