Genotype information on repeat polymorphisms (microsatellites) was available for the DRD4 (exon 3, VNTR), the DAT1/SLC6A3 (3' untranslated region VNTR) and the SERT/SLC6A4 (a VNTR in intron 2: STin2) and an in/del promoter polymorphism (5-HTTLPR) from an analysis based on 1116 ADHD families. Here, SLC6A4 is linked to attention deficit-hyperactivity disorder.