ObjectiveTo observe the effects of chemotherapy on mitochondria ultrarnicrostructure and stereological characteristic of mucinous cystadenocarcinoma (MC) and serous cystadenocarcinoma (SC) and to investigate clinical significance and possible mechanism of chemotherapy on two cystadenocarcinoma.MethodsThe ultramicrostructure changes of mitochondrion were observed with electronic microscope and the stereological changes and its interrelation of volume density (Vv), surface density (Sv) and ratio of surface density(Rsv,μm-1)of mitochondria of the cells in ovarian carcinoma were studied and compared with the normal control. ResultsElectron microscope reveals that the mitochondria swelling and cristae disorganizing were seen in ovarian carcinoma.The Vv(0.072±0.059)and Sv(0.057±0.040)of MC mitochondria were decreased markedly(P =0.004 and P =0.029, respectively), while its Rsv (0.891 ±0.400) μm-1 increased obviously (P =0.015); but the Vv and Sv of mitochondria of the SC cells were increased markedly (0.267±0.12,P =0.001 and 0.122±0.057,P =0.003,respectively).After chemotherapy,cancer cells mitochondrion Sv elevated significantly (0.060±0.037, P = 0.053), showing a similar MC mitochondria of variability. Conclusion Therearedifferentcharacteristicsintheultramicrostructureandstereologicalcharacteristicinthe mitochondria of two types ovarian carcinoma. Effects of chemotherapy may be associated with the ameliorate of construction and function of ovary cells.