Single nucleotide polymorphisms (SNPs) are the most abundant form of genetic variation in the human genome, accounting for more than 90% of all differences between individuals. Many complex phenotypes in humans have a significant genetic component and most of the variability is therefore likely to stem from differences in patterns of SNPs. Association studies involving the large-scale analysis of SNPs can help to identify genes affecting many human phenotype variations, including complex diseases and drug responses. SNPs therefore play a major role in all stages of the drug development process, from target identification through to clinical trials. SNPs are also the basis of pharmacogenomics, the tailoring of medicines to suit an individual's genome. Given the potential impact of SNPs on healthcare, the biotechnology industry has focussed urgently on the development of high-throughput methods for SNP genotyping. All genotyping methods are a mix and match of different allele discrimination and signal detection technologies and as such may represent the intellectual property of several individuals or organizations. In this review, we explore the patent issues surrounding SNP genotyping and how this is influencing large scale, commercially valuable projects involving SNPs.