BACKGROUND A single nucleotide polymorphism (SNP) in the stromal cell-derived factor-1 (SDF-1) gene at position 801 (G>A) is associated with susceptibility to certain tumors. This study aimed to investigate an association between this SNP and colorectal and gastric cancers in an Iranian population. METHOD Genotype and allele frequencies of SDF-1 801 G>A were assessed using polymerase chain reaction-restriction fragment length polymorphism in 109 patients with colorectal cancer, 124 with gastric cancer, and 262 normal control volunteers. RESULTS No statistically significant difference was observed in the frequencies of genotypes and alleles between patients and controls (p > 0.05). CONCLUSION SDF-1 gene polymorphism at position 801 (G>A) was not associated with colorectal and gastric cancers in Southern Iranian patients.