Chemokine (C-C motif) ligand 24 (CCL24, eotaxin-2) is a CC chemokine that recruits and activates cells bearing the CC chemokine receptor 3, which play a major role in asthma. Previously, we observed a significant association between a single nucleotide polymorphism (SNP) in eotaxin-2 (CCL24+1272A--> G) and a lower risk of asthma. Consequently, this study has followed up on those genetic effects by evaluating the association between the SNP and plasma eotaxin-2 concentration in 172 asthmatics and 135 normal controls. Asthmatics had significantly higher plasma eotaxin-2 levels than did normal controls (P=0.02). The SNP (CCL24+1272A--> G) and two haplotypes (ht2 and ht6) were strongly associated with plasma eotaxin-2 levels in asthmatics (CCL24+1272A--> G: P=0.006, ht2: P=0.006, and ht6: P=0.002). The CCL24+1272A--> G allele and the ht2 and ht6 haplotypes showed a gene-dose effect on the plasma eotaxin-2 levels in asthmatics (P=0.005-0.032). In conclusion, the susceptibility of patients with asthma to high eotaxin-2 production may be due to genetic effects of the CCL24+1272A--> G polymorphism, ht2 and ht6 haplotypes.