The main objective of this proficiency test (PT) is to provide interested laboratories with an opportunity to test their multi-mycotoxin methods on 12 mycotoxins and 3 sums of mycotoxins at the same time on oat flour and to compare their interlaboratory results. The PT allowed the determination of the following toxins: aflatoxin B1 (AfB1), aflatoxin B2 (AfB2), aflatoxin G1 (AfG1), aflatoxin G2 (AfG2), ochratoxin A (OTA), fumonisin B1 (FB1), fumonisin B1 (FB2), fumonisin B3 (FB3), zearalenone (ZEN), deoxynivalenol (DON), T2-toxin (T2), HT2-toxin (HT2). In addition, three sums of mycotoxins were included: the sum of FB1 and FB2, the sum of the aflatoxins (AfB1, AfB2, AfG1 & AfG2) and the sum of T2 & HT2 toxin. 24 participants were accounted for of which one participant chose to report with two different methods and which will be counted as a separate participation so 25 results in total are used for the report. Participants were invited to report the mean value and measurement uncertainty of their results. The assigned values (Vass) and their uncertainties (u(xa)) were determined as the consensus of participantsí results. Standard deviations for proficiency assessment were calculated using the modified Horwitz equation.