DNA microarrays, or biochips, are small glass chips embedded with ordered rows of DNA and by providing a massive parallel platform for data gathering represent a fundamental technical advance in biomedical research. Such biochips enable the use of advanced fabrication, detection, and data mining technologies that allow data gathering at an unprecedented rate. The first chapter is an introduction to the technology of DNA microarrays, emphasizing the methodological fundamentals of biochips. The next two chapters describe the use of confocal scanning in microarray detection and techniques for the efficient cloning and screening of differentially expressed genes. Chapter 4 describes assay optimization for enzymatic assays and chapter 5 antisense scanning arrays. This is followed by a chapter on the manufacture of molecular arrays using ink-jet printing technology. Chapter 7 describes gene expression analysis from cDNA microarrays and then chapter 8 covers the use of expression data in bioinformatics. Chapter 9 describes the use of active microelectronic arrays for DNA hybridization analysis and the last chapter details the use of microarray technology in pharmacogenomics. This Practical Approach book is a comprehensive overview of the new and expanding field of DNA microarray technology and will be invaluable to any researcher interested in the use of biochips.