Molecular imprinting leads to functional polymers that are capable to incorporate the template used and thus lead to selective chemical sensor systems when combined with a suitable transducer. Benzene and xylene can e.g. be distinguished with a selectivity factor of nearly ten using mass-sensitive devices such as QCM and SAW, although they both contain an aromatic system and differ only by the methyl groups. Sensing materials are further tuned by using binary mixtures as templates. When analyzing polycyclic aromatic hydrocarbons (PAH) by fluorescence and QCM measurements, the sensitivity is substantially increased if a second template molecule is applied as a porogen. Capacitive sensor measurements on polymers imprinted with microorganisms, such as yeasts, show substantial sensor responses due to highly selective inclusion compared with a non-functionalised surface yielding only negligible effects.