Six companies/research institutes have participated in a Round Robin test concerning measurements of Flow Rate Ratio (FRR). A draft Nordtest method regarding FRR and polyethylene is partly based on the Round Robin. A flow rate ratio is obtained by dividing the flow rate at one condition by the flow rate at another condition. The reproducibility and the effect of melting time on the results has been investigated. Studies were also performed on the effects of the charged amount of material on the FRR results. All materials were polyethylenes with various densities and different amounts and types of additives. Two different loads at testing of each material has been used. The loads were selected together with the producer of the materials. For materials with high density two melting times were used, 4 minutes and 8 minutes, in order to find out if materials with high density sufficiently heated at the start of measurements. The Round Robin showed that a melting time of 4 minutes reached the same result as a melting time of 8 minutes. Consequently we see no reason to discriminate different densities of the polyethylenes. The amount of material that has been charged into the cylinder has been annotated during the test. The results show the amount of material does effect the result. However to draw any conclusions based on this Round Robin is not possible. No univocal trend is found. MFR respectively FRR have good reproducibility. For material with high MFR values the deviation tend to be bigger than for lower values. MFR obtained using a small load is often close to zero shear viscosity of the material. FRR is favorable for separating material that has just about the same MFR.