The Round Robin test for 2009 is organized by RIZA in the Netherlands. SINTEF has followed the analysis and data treatment as described in the revised CEN-part 2 guideline (CEN/TR 15522-2:2009), November 2009. The GC/MS analysis were performed using 30m column. The following conclutions can be drawn from the oil comparison study:• Source sample 1 (bilge sample) is found to be a positive match to source sample 2, 3, 4 and with spill sample 6. • Source sample 1 and spill sample 5 has two diagnostic ratios (m/z 216) higher that the limit of 14 %. Based on the criteria in the CEN-guideline we can not conclude with positive match between sample 1 and sample 5, according to “several ratio > r95%”. In this case we conclude a possible match between sample 1 and sample 5. Based on earlier experiences and discussion in the OSINET working group has indicated differences between samples in the m/z 216 pattern even the two samples positively are from the same origin, and this observaton may be explained that m/z 216 may not be resistant to e.g. photo-oxidation, but need to be further investigated. It is therefore still likely that suspected bilge from the ship can be the source of sample 5, anyway.