Novel thrombin selective inhibitors incorporating the azaphenylalanine scaffold or partially saturated heterobicyclic P1 arginine mimetics were developed. X-ray crystal structures of some inhibitors co-crystallized with human thrombin was determined. Novel types of peptidomimetic fibrinogen receptor antagonists mimicking the RGD sequence are an important contribution to a research of novel antiaggregatory drugs. A new type of antithrombotic compounds with a dual mechanism of action, i.e. acting as trrombin inhibitors and fibrinogen receptor antagonists were discovered. Novel inhibitors of Mur X enzymes as potential new antibacterial agens inhibiting the biosynthesis of peptidoglycan were studied. The antibacterials which will result from this research will enable a more efficient therapy of infections and provide a basis for the study of bacterial resistence on a molecular level. New mimetics of RGD sequence contribute to understanding of the structure-activity relationship among ligands of integrins and provide information on the receptor topography. Novel selective thrombin inhibitors provide new information on structure-activity relationship in this class of compounds. New peptidomimetic scaffolds and new synthons for the construction of peptidomimetics are a contribution to basic research in the field of medicinal chemistry. Covalent binding of clenbuterol derivatives to a beta lactamase mutant is opening a possibility for immunological determination of traces of clenbuterol in meat. New nitroxide spin labels resulting from this programme offer a potential for the study of structure and dynamics of outer membrane surface which will contribute to understanding of intercellular interactions. A validated HPLC method was developed for studying oxidative transformations of dithranol within the first hour after exposure to oxidative environment. It will contribute to understanding of oxidative transformation of dithranol. Our discovery of new mutations (P325P in ER alpha, V328V in ER beta), and new gene polyimorphisms in a promotor region of the gene for OPG (209GtoA, 245TtoG, 889CtoT in 950 TtoC) and assessment of their influence on a mineral bone density contribute to understanding of a role of gene factors in development of osteoporosis.