The natural origin of natural rubber causes routine shipments of raw NR to be potentially one of the most variable raw materials which can be used in the tire production process. The RPA 2000® Rubber Process Analyzer can be used to quantify this variability in order to implement changes in mixing and processing and improve the ultimate tire quality and uniformity. This study is the result of a tire factory investigation of natural rubber variation using the RPA. A rapid 2-minute test programmed on the RPA Auto was found to be very effective and practical for testing the quality of both raw natural rubber bales and factory mixed stocks. RP A data showed the % Range of Variation to be as high as 24 % for within bale variation, and as high as 42 % for variability between bales. The RP A at high strain testing conditions gave very good statistical test sensitivity (signal-to-noise) to natural rubber variation. Also it was observed that natural rubber variation is due more to changes in its elastic quality than viscosity differences. In addition, it was found that this natural rubber variability significantly contributed to batch-to-batch variation of factory mixed stocks, even though the magnitude of this variation is somewhat reduced by additional "passes" (increased work history from multiple pass mixing). Lastly, the RPA dynamic properties of the raw natural rubber were found to be statistically related to the quality of mix. This study clearly shows that NR properties directly influence both the mixing cycle and the mixed physical properties. So through proper use of the RPA, better batch-to-batch uniformity can be achieved.