The use of a molecularly imprinted polymer (MIP) as a selective surface for ambient mass spectrometry is demonstrated. The MIP is used to sequester target analytes from urine and easy ambient sonic-spray ionization mass spectrometry (EASI-MS) is shown to be able to efficiently desorb the analytes from the MIP surface and then transfer them in protonated forms to the gas phase for MS analysis. A set of five phenothiazines (chlorpromazine, perphenazine, triflupromazine, thioridazine and prochlorperazine) were chosen from a proof-of-principle class of drug samples. A chlorpromazine-imprinted methacrylic polymer was synthesized and used to prepare a MIP probe. The MIP-EASI-MS technique using acidified methanol as solvent has been shown to allow quantification of all five drugs in urine with LOQ of ca. 1 micromol L(-1).