Medroxyprogesterone acetate (MPA) which has a steroid structure, is widely used in oncology practice in the treatment of the cachexia of cancer and to reduce hematologic toxicity in patients receiving chemotherapy. However, the mechanisms of MPA on these effects are unclear. In this study, we investigated the effects of two different doses of MPA (10(-5) and 10(-6) M/L) on acidic pH induced apoptosis of periferal blood mononuclear cells (PBMC) derived from 10 healthy volunteers. Compared with the control group, we found that MPA at the dose of 10(-5) M/L had a negative effect on apoptosis (32.88 +/- 4.61 and 20.7 +/- 1.53% respectively, p < 0.05), a positive effect on cell count of PBMC (1395 +/- 151 x 10(3) and 1100 +/- 139 x 10(3) respectively, p < 0.05) and no effects on cell viability and its proliferation. More comprehensive trials are needed to clarify this effect of MPA.