Abstract: SPME is a sample pretreatment method which combines sample clean-up, concentration and introduction of the extract into the separation system. In order to evaluate the efficiency of molecularly imprinted polymers (MIPs) fibers were coated with a 100-mm thick layer of clenbuterol imprinted polymer. Cross reactivities were investigated using structure analogs of clenbuterol (brombuterol, formoterol, timolol) and four weakly basic compounds (amphetamine, codeine, diazepam, atrazine). The analytes were extracted from buffer solutions in order to investigate the non-selective interaction and extracted from acetonitrile in order to investigate the selective interaction. After extraction, the analytes were desorbed from the fiber in 1 mM hydrochloric acid in methanol and analysed by LC-ECD (electrochemical detection) and LC-MS-MS (electrospray/ion trap mass spectrometry). Results show the large differences in partition coefficients for the test components for the blank and imprinted fiber. This information was used to prove the suitability of MIPs for selective extraction of clenbuterol.