In order to evaluate the combined effect of Amifostine and Merocyanine 540 during photoirradiation in neoplastic cells, bone marrow cells from children with acute leukemia (AL), age-matched controls as well as HL-60 cell line were studied. Cell suspensions were incubated with Amifostine, then with MC 540 and they were subsequently exposed to different irradiation doses by Argon Laser 514 nm. Cell survival was estimated by trypan blue supravital stain following a 24-h incubation. The leukemic cell line was studied in continuous liquid cell cultures for 4 weeks. The survival of normal bone marrow progenitors has been estimated by colony formation assay in methylcellulose cultures. Our results showed that Amifostine enhances the photokilling effect of MC 540 on leukemic cells and significantly protects bone marrow nucleated and committed progenitors (BFU-E and CFU-GM) from children with AL under chemotherapy. In conclusion, Amifostine seems to be a promising cytoprotective agent in the clinical use of purging with MC 540 mediated phototherapy.