Serotonin is a pulmonary vasoconstrictor and smooth muscle cell mitogen. The serotonin transporter (SERT) is abundant in pulmonary vascular smooth muscle. Compared with the short (S) allele, the long (L) SERT promoter allele is associated with increased SERT transcription and more severe pulmonary hypertension in a cohort of patients with chronic obstructive pulmonary disease, and was more prevalent in a cohort with idiopathic pulmonary arterial hypertension (IPAH), compared with control subjects.We hypothesized that the SERT L allele would associate with an earlier age at diagnosis and/or shorter survival interval in pulmonary arterial hypertension (PAH) than the S allele.SERT promoters from 166 familial PAH (FPAH), 83 IPAH, and 125 control subjects were sequenced. One hundred twenty-seven of the patients with FPAH had a known mutation in bone morphogenetic protein receptor 2 (BMPR2).The mean age at diagnosis was 35.8 yr in patients with FPAH and 41.1 yr in patients with IPAH (p = 0.02). There were no significant differences in distribution of the LL, LS, or SS genotypes in IPAH, FPAH, or unaffected BMPR2 mutation carriers. In FPAH, the LL genotype was associated with an earlier age at diagnosis (p < 0.02).In patients with IPAH, these SERT genotypes do not correlate with age at diagnosis or survival interval. In patients with FPAH, the LL genotype correlates with an earlier age at diagnosis than SL or SS, although survival among the groups was similar. The correlation of the SERT promoter polymorphism with age at diagnosis in FPAH suggests a possible relationship between the SERT and BMPR2.