The present study was undertaken to explore the effect of administration of high doses of sodium selenite on the apoptosis of lymphoma cells in patients with non-Hodgkin's lymphoma (NHL). Forty patients with newly diagnosed NHL were randomly divided into two groups. Group I received standard chemotherapy, whereas group II received adjuvant sodium selenite 0.2 mg kg(-1) day(-1) for 7 days in addition to chemotherapy. Flow cytometry was used for monitoring of lymphoma cells apoptosis at the time of diagnosis and after therapy in the two groups. Sodium selenite administration resulted in significant increase in percentage of apoptotic lymphoma cells after therapy in group II (78.9 +/- 13.3% versus 58.9 +/- 18.9%, p < 0.05). In addition, patients who received sodium selenite treatment demonstrated statistically significant increase in percentage of reduction of cervical and axillary lymphadenopathy, decrease in splenic size, and decreased percentage of bone marrow infiltration. Also, we found a statistically significant decrease in cardiac ejection fraction (CEF) in group I and no reduction in CEF in patients who received sodium selenite 'group II', denoting the cardioprotective effect of selenium. It is concluded that sodium selenite administration at the dosage and duration chosen has synergistic effect to chemotherapy in inducing apoptosis and, consequently, could improve clinical outcome.