Topical drug delivery has become one ofthe most exciting and challenging areas of pharmaceutical research in the last decade. Topical drugs encompass both dermal and transdermal products, which are used for local and systemic effects, respectively. This volume succinctly discusses different aspects of dermal and transdermal drug delivery and represents the state of the art and science in mea- suring percutaneous penetration and in determining biological relevance. The topics covered are of importance for both basic research and clinical applications, for example, cutaneous bioavailability and bioequivalence. Signif- icant areas discussed include dermal and transdermal drug delivery, in vitro and in vivo methodology to assessbioavailability and bioequivalence oftopical drug products, in vitro and in vivo correlations, and pharmacokinetic and pharma- codynamic modeling. Also covered are regulatory considerations for the drug approval process and requirements for all topical drug products. Many of the complex issuesinvolved in the evaluation of both innovator and generic products are identified and explained as well. This reference guide will be a useful basic working tool for investigators, and will be a valuable asset to all pharmaceutical scientists involved in the development of topical drug products.