the best utilization of raw material for manufacturing the optimum quality of yarn has become inevitable for the spinning mills to face the global competition. mechanical properties of yarn are of the most important properties from quality point of view and largely depend upon the fiber length and micronair value ; which are considered the foremost quality parameters for the selection of raw material . it is the purpose of this study to investigate the effect of cottons differing fiber length and micronair value on mechanical propeties of yarn so as to contribute in determining the optimum using of the raw material .