Objective:　The　present　study　aims　to　investigate　the　relationship　between　genetic　polymorphisms　in　HTR3A　and　HTR3E　and　diarrhea　predominant　irritable　bowel　syndrome　(D-IBS)　in　a　Chinese　population.　Methods:　We　enrolled　500　D-IBS　patients　and　500　age-and　sex-matched　healthy　control　subjects　to　detect　the　genotypes　in　HTR3A　and　HTR3B　gene　by　using　of　PCR-RFLP　method.　Results:　There　were　significant　difference　between　the　D-IBS　patients　and　the　health　control　subjects　in　the　distribution　of　genotype　and　allele　of　rs1062613　in　HTR3A　gene.　As　regarding　rs62625044　in　HTR3E　gene,　we　found　there　was　a　significant　different　between　the　case　and　the　control　group　in　the　distribution　of　GA　genotype　and　A　allele　in　female　but　not　in　male.　Conclusion:　The　present　study　suggested　that　there　are　associations　of　D-IBS　risk　with　genetic　polymorphisms　in　HTR3A　and　HTR3E.