Dysfunction of the serotonergic system has been hypothesized to play an important role in panic disorder. We investigated the 5-HT2A receptor (5HTR2A) and tryptophan hydroxylase (TPH) genes for an association with panic disorder (PD). Patients with PD (n=107) and control subjects (n=161) were genotyped for 5HTR2A 1438A/G, 5HTR2A 102T/C, and TPH218 A/C. The severity of their symptoms was measured using the Spielberger State-Trait Anxiety Inventory (STAI), Panic Disorder Severity Scale (PDSS), Anxiety Sensitivity Index (ASI), Acute Panic Inventory (API), and Hamilton's Rating Scale for Depression (HAMD). There were no significant differences in the genotype distributions or allelic frequencies in the three serotonergic polymorphisms between PD patients and normal controls. However, we found a significant difference in symptom severity among the genotypes of both the 5HTR2A 1438A/G and 102T/C polymorphisms. Although there were no significant differences in the genotype and allele distributions, we found a significant association between panic symptom severity and the serotonin 2A receptor gene. This result suggests that 5HTR2A 1438A/G and 102T/C polymorphic regions can be associated with the phenotype or the pathogenesis of panic disorder.