After a brief account of the two main DNA microarray technologies in use - Affymetrix's GeneChip#8482; arrays and cDNA microarrays - this technology focus looks first at the expansion of the market for these platforms from a purely research base. The main areas of biomedical research undertaken using DNA microarrays are then outlined (gene expression profiling, comparative genomic hybridisation and the analysis of single nucleotide polymorphisms), and the use of the arrays is discussed in drug discovery and in the development of diagnostics. Examples are included of deals concerning DNA microarray technology that have been struck in these areas.