Polymorphisms within the Dopamine Transporter Gene (SLC6A3 or DAT1) are needed for genetic analyses of dopamine-related traits including addiction. We screened the gene looking for Single Nucleotide Polymorphisms (SNPs), using Polymerase Chain Reactions (PCRs) and restriction endonuclease digestion. Sites in which cutting occurs in some individuals’ DNA but not others are polymorphic and will be cataloged for future genetic analyses. This method allowed detection of other types of polymorphisms as well (e.g., tandem repeat variations).