Preface (B. Testa) SETTING THE SCENE Pharmacokinetic Challenges in Lead Optimization (G. Gaviraghi, R.J. Barnaby and M. Pellegatti) Modelling in Preclinical and Clinical Drug Development (L.P. Balant and M. Gex Fabry) MOLECULAR AND BIOLOGICAL BACKGROUND Structure of Liposomal Membranes in Relation to Permeation (O.G. Mouritsen, H.K. Andersen, J.S. Andersen, J. Davidsen, L.K. Nielsen and K. J?rgensen) Relations of Molecular Properties with Drug Disposition: The Cases of Gastrointestinal Absorption and Brain Penetration (H. van de Waterbeemd and D.A. Smith) Structure Metabolism Relations, and the Challenge of redicting Biotransformation (B. Testa and G. Cruciani) Concepts in Prodrug Design to Overcome Pharmacokinetic Problems (B. Testa and J.M. Mayer) BIOLOGICAL STRATEGIES Methodologies in Cell Culture (H. Wunderli Allenspach) Biological Models to Assess Drug Bioavailability (R.T. Borchardt) Biological Models to Study Blood Brain Barrier Permeation (S.D. Kramer, N.J. Abbott and D.J. Begley) Biological Models to Study Skin Permeation (N. Sekkat and R.H. Guy) Biopharmaceutical Aspects of Nasal and Pulmonary Drug Delivery (P. Colombo, D. Cocconi, P. Santi, R. Bettini, G. Massimo, P.L. Catellani and C. Terzano) Significance of Plasma Protein Binding in Drug Research (S. Urien, J. P. Tillement and J. Barre) High Throughput ADE Screening (O. Kretz and A. Probst) In Vitro Models for Early Studies of Drug Metabolism (J.H. Lin and A.D. Rodrigues) Addressing Toxicological Issues in the Lead Optimization Phase of Drug Discovery and Evelopment (P. Bentley) PHYSICOCHEMICAL STRATEGIES Physicochemical Parameters as Tools in Drug Discovery and Lead Optimization (B. Faller and F. Wohnsland) Lipophilicity profiles: theory and measurement (J. Comer and K. Tam) High Throughput Measurements of Solubility Profiles (A. Avdeef) Cyclic voltammetry as a new tool to study the partitioning and proton transport behaviour of ionized drugs (F. Reymond, G. Bouchard and H. Girault) Biolipid pKas and the Lipophilicity of Ampholytes and Ion Pairs (R.A. Scherrer) Recent Advances in Reversed Phase HPLC Techniques to Determine Lipophilicity (C. Yamagami) Liposome / Water Partitioning: Theory, Techniques and Applications (S.D. Kramer) Importance of the Mobile Phase in Immobilized Artificial Membrane Chromatography (K.L. Hauer and C. Pidgeon) High Throughput Artificial Membrane Permeability Studies In Early Lead Discovery and Development (M. Kansy, H. Fischer, K. Kratzat, F. Senner, B. Wagner and I. Parrilla) NMR Spectroscopy for the Study of Drug Phospholipid Interactions (R. Fruttero) COMPUTATIONAL STRATEGIES Virtual Screening of Molecular Properties: A Comparison of Log P Calculators (M.E. Duban, M.G. Bures, J. DeLazzer and Y.C. Martin) Quantitative Structure Absorption Relationships (H.van de Waterbeemd) Hydrogen Bonding, the Last Mystery in Drug Design? (H. Kubinyi) Molecular Hydrogen Bonding Potentials (MHBPs) in Structure Permeation Relations (G. Caron, S. Rey, G. Ermondi, P. Crivori, P. Gaillard, P. A. Carrupt and B. Testa) VolSurf and its Interest in Structure Disposition Relationships (G. Cruciani, S. Clementi, P. Crivori, P. A. Carrupt and B. Testa) Molecular Modeling Approaches to Predict Metabolism and Toxicity (A.M. ter Laak and N.P.E. Vermeulen) CONCLUSION Molecular Biology, Drug Design and Drug Delivery: Bringing It All Together (V.H.L. Lee, S.K. Wu and C. Chu) Pharmacokinetic lead optimization: fine art vs. blind technology (B. Testa)