The first world-wide interlaboratory study on PBDEs, organised between November 1999 and April 2000, involved five biological samples, two sediments and two standard solutions. These materials were sent to 26 participants in nine different countries. Results were returned from 18 laboratories. The results reported for BDE 47 were acceptable with a range of relative standard deviations (Rsd) of 17–40%. Results for the BDEs 99 (Rsd 25–77%), BDE 100 (Rsd 19–48%), 153 (Rsd 30–48%) and 154 (Rsd 25–43%) showed that a further improvement of these analyses is needed. The BDE 209 analysis is not under the control of the participating laboratories. The data reported for the biota samples were very variable and for the two sediments Rsd values of 48% and 78% were obtained. It is recommended that analysts pay more attention to the special requirements for the BDE 209 analysis such as avoiding exposure to intensive light and exposure for too long times to too high temperatures.