Objective:TounderstandthechangeofTh1/Th2andTc1/Tc2balanceinpatientswithsecondaryearlysyphilis.Methods:PeripheralbloodThandTccellsubpopulationswereexaminedbythree-colorflowcytometryin30patientswithsecondaryearlysyphilisand20healthysubjects.Results:PercentagesofCD3^+,CD4^+TcellsandtheratioofCD4^+/CD8^+andNKcellsinsyphiliticpatientsweresignificantlylowerthaninthecontrolgroup(P<0.001),butnostatisticaldifferencewasfoundinpercentagesofCD8^+andCD19^+cellsbetweenthetwogroups(P>0.05).ThepercentageofTh1cellsandratiosofThl/Th2andTcl/Tc2insyphiliticpatientswereclearlydecreasedascomparedtothoseincontrois(P<0.001-0.01),whereaspercentagesofTc0andTc2cellsinsyphiliticswashigherthanthoseincontrols(P<0.001).Conclusion:Therecouldbeadisturbanceofcellularimmunityandtherelativelyintactfunctionofhumoralimmunityinsecondarysyphilis.ItispostulatedthatthepolarizationtowarddevelopmentofTh2andTc2cellsandtheirassociatedcytokinesmightbeinvolvedintheincompleteclearanceoftreponemesandthedevelopmentofchronicinfection.