Objective:The role of methylseleninic acid (MSeA), a selenium compound, has been documented in cancer chemoprevention. However, the therapeutic effect of MSeA in combination with paclitaxel, a chemotherapeutic agent used to treat ovarian cancer, is unknown. In this study, we investigated the effect of combination treatment of MSeA and paclitaxel against ovarian cancer cells. Methods:Ovarian cancer cells(A2780) were treated with different concentrations of MSeA, paclitaxel alone or in combination. The individual and combined concentrations of drugs that achieved certain cells growth/death were determined using a sulforhodamine B(SRB) assay. Drug effects on cell viability were further confirmed using floating cell count and trypan blue exclusion assay. The mean values±standard deviation were calculated and compared between treatment groups using unpaired t test. Results: The concentration of paclitaxel alone that inhibited 50% of cell growth(IC50) was 0.5μmol/L. This concentration increased to 1.2μmol/L when paclitaxel was given in sequential combination with MSeA. The number of dead cells after the combination treatment did not show a significance increase when compared with drug alone. Conclusion:Pretreatment with MSeA did not enhance the paclitaxel effect against A2780 ovarian cancer cells.