Previous research identified a highly polymorphic site between intron 6 and intron 8 of the human DAT1 gene. The experiment attempt to identify the cause of this polymorphism. A region in intron 8 has shown great difficulty to amplify even with multiple attempts with different DNA polymerase enzymes and various additives to improve the experiment. Isolating and sequencing the fragments from polyacrylamide gels are the next steps to analyze the site.