To investigate the impacts of gene variations on survival outcomes of advanced gastric cancer (AGC) patients treated with 5‑fluorouracil (5-FU)-based chemotherapy, we analyzed the associations of 2 indels of the TS gene rs34743033 (double or triple tandem repeats of a 28 bp sequence in 5'-UTR, denoted as 2R or 3R allele) and rs16430 (a 6 bp variation at 1494 bp in 3'-UTR, denoted as ins6 or del6 allele) and 2 single nucleotide polymorphisms (SNPs) of ABCB1gene rs2032582 in exon 21 and rs1045642 in exon 26, with clinical outcomes after 5‑FU treatment.