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Objective: This study was designed to examine the role of DNA variants of the dopamine D4 receptor gene (DRD4) in smoking experimentation in adolescents and to determine the extent to which novelty seeking (NS) could account for a possible effect of DRD4 on tobacco use., Method: Participants were from a longitudinal study of an original birth cohort (born 1986-1988) of 384 children from a high-risk community sample. At age 15 years, adolescents completed a self-report questionnaire measuring tobacco consumption and temperament (Junior Temperament and Character Inventory). DNA was taken from 303 participants (144 males, 159 females) and genotyped for the DRD4 exon III polymorphism., Results: DRD4 was associated with smoking status and NS in males but not in females. Males with the seven repeat allele exhibited more smoking involvement (p < .002) and scored higher in NS (p < .002) than males without this allele. In addition, elevated tobacco use was related to a higher level of NS in both males and females (p < .001). Multiple regression analyses revealed that NS mediated the relationship between DRD4 and smoking in males., Conclusions: These findings highlight the importance of considering the mechanisms underlying the association between genetic factors and tobacco use separately by gender and, possibly, by developmental period.