Over the past ten years, sophisticated in vitro test systems based on epithelial cell cultures have been introduced in the field of drug delivery. These models have been very useful in characterizing the permeability of drugs across epithelial tissues, and in studying carrier systems for improved drug delivery and enhanced absorption. Compared to in vivo trials, cell culture models are faster, more convenient and cost effective, ethically advantageous, and more easily standardized. This book provides a practical approach to such in vitro techniques. It is an invaluable source of information for graduate students and pharmaceutical scientists in industry or in academia.