The study findings provide preliminary evidence of genetic influences on various stages of smoking and suggest the importance of specific dopamine genes in smoking progression in adolescence. Smoking initiation was related to allelic variation in the dopamine D4 receptor gene (DRD4); whereas smoking continuation and dependence showed association with the dopamine D2 receptor gene (DRD2). Adolescents with the seven-repeat allele of the common DRD4 exon 3 polymorphism had rates of "ever smoking" that were significantly higher than in those with other genotypes. Once smoking started, carriers of the T allele of a single nucleotide polymorphism of DRD2 (rs4648317) reported higher rates of current smoking and scored higher on nicotine dependence than their allelic counterparts. Among current smokers, intention to quit was significantly lower in adolescents homozygous for the 10-repeat allele of the common dopamine transporter 3 untranslated region polymorphism. Data were drawn from an ongoing prospective study of the long-term outcome of early risk factors studied since birth. At 15 years old, 220 participants (108 males and 112 females) completed a self-report questionnaire that measured smoking behavior. They were genotyped for five dopamine gene variants. 3 tables and 47 references