Disorders of speech and language development can sometimes result from rare mutations that have dramatic effects on gene function. In 2001 Dr. Fisher and his colleagues discovered a point mutation disrupting the FOXP2 gene in fifteen members of a large family from the UK. The affected people have problems sequencing mouth movements during speech, accompanied by difficulties with both expression and reception of language. Further investigations uncovered distinct mutations of FOXP2 in other families with similar speech and language deficits, but suggested that damage to this gene may only account for less than 2% of such cases in the population. It is very likely that rare mutations in other genes, apart from FOXP2, are also able to cause severe language problems. The advent of high-throughput DNA sequencing provides exciting new opportunities for tracking down these additional language-related genes. Our first work in this area involves sequencing the entire exome – all parts of the genome that code for proteins – in children with severe language problems, and in extended families in which speech and language problems are inherited by many relatives. We are currently sequencing the exomes of 50 children with severe language impairment, to identify new mutations in genes that may cause their disorder.