Radioprotective effects of amifostine and melatonin as well as their ability to modulate the level of spontaneous and gamma-irradiation-induced genetic changes on human peripheral blood lymphocytes were investigated using the cytokinesis-block micronucleus (CBMN) assay and sister chromatid exchange (SCE). Parallel blood samples were pre-treated with amifostine, melatonin and their combination for 30 minutes. Negative controls were also included. After the treatment with radioprotectors, one blood sample of each experimental group was exposed to gamma-rays from a 60Co source. The radiation dose absorbed was 2 Gy. Our research confirmed the radioprotective effects of both chemicals in vitro, with no significant genotoxicity. Pre-treated irradiated blood samples showed a decrease in the total number of micronuclei (MN) and in the number of cells with more than one MN. They also showed significantly lower mean SCE values. This study shows that it is possible combine these radioprotectors by adjusting the doses of amifostine to achieve the best radioprotective effect with as few side effects as possible. However, further in vitro and clinical studies are needed to clarify their mechanisms of action and possible interactions.