Abstract: We have recently developed an HPLC based sensor for the antibiotic choramphenicol whereby a dye conjugate is displaced from a molecularly imprinted polymer (MIP) by the substrate. The sensor is immune to interference from chloramphenicol derivatives and is only one third as responsive to thiamphenicol, an almost identical analogue. The dynamic range of the system easily spans the theraputic range of the drug arid further applications of this system will be discussed. Other work concerns the development of an artificial steroid receptor which is selective for testosterone. We have thoroughly investigated the effect of various polymerization conditions on the selectivity of the MIP and will discuss the implications. Furthermore, we report a novel post polymerization treatment by which the selectivity of this polymer can be further enhanced