The antioxidant effects of Calcium Dobesilate (CD, Doxium) were investigated in relation to the oxidative status, apoptosis and in vitro proliferation of human peripheral blood mononuclear cells (PBMC) isolated from healthy donors. CD alone did not modify cell growth in vitrountil 10 microM. This molecule counteracted oxidative damages generated by the high reducing sugar dR and was shown to reduce apoptosis by delaying both membrane permeability changes and DNA fragmentation. CD 10 microM affected in a time-dependent dynamics several parameters representative of the cellular oxidative status. In particular, CD significantly increased the activity of glutathione S-transferase (GST) after three days of treatment and also, but to a lower extent, the activity of gamma-glutamyltransferase (gamma-GT). Both enzymes are known to be involved in the glutathione (GSH) metabolic cycle. This enzymatic behaviour was reversed at seven days of treatment, with a significant GST decrease and a gamma-GT activation. After seven days of CD exposure, the intracellular GSH content was enhanced and this resulted in a dramatic decrease in lipid peroxidation, underlining the powerful antioxidant properties of CD in human PBMC.