Eukaryotic pre-mRNA splicing allows for a large, diverse proteome to be coded by a relatively small genome. Alternative splicing events are well regulated, but when mutations disrupt the splice sites or regulatory elements, disease can occur. Similarly, mutations can cause disease through aberrant transcript production. Enhancers, one of the splicing regulatory elements, are frequent targets of disease causing mutations. This review provides an overview of the splicing reaction and mechanisms of alternative splicing and provides examples of enhancer defects that cause disease.