DNA analysis is a subject that is in the news almost every day, whether it be a new advance in medical research, a criminal trial, or some other application. BLAST (Basic Local Alignment Search Tool) is an important program used by biologists worldwide to compare DNA and protein sequences and to infer functional and evolutionary relationships between them. In this talk, we will examine several methods of aligning DNA sequences, and will look at the some of the algorithmic details underlying the implementation of BLAST.