Among the 161 cases of pT1 ovarian cancer treated at our hospital during the last 25 years, the impact of systematic lymphadenectomy was evaluated in 93 cases of the pT1N0M0 group(N0 group), 59 cases of the pT1NxM0(Nx group), and 9 cases of the pT1N1M0(N1 group). Significantly greater relapse-free survival(RFS)and overall survival(OS)were observed in 108 cases of the N0+N1 group compared to the Nx group(p=0. 006, p=0. 02). Multivariate analysis showed that systematic lymphadenectomy was a significant prognostic factor(hazard ratio 0. 473(95%CI, 0. 235-0. 951; p=0. 036). The present study suggested the systematic lymphadenectomy had a significant therapeutic effect on pT1 stage ovarian cancers.