Objective: Modern people are exposed to many environmental factors, including Extremely Low-Frequency Magnetic Fields (ELF-MF). ELF-MFs are emitted from everything that produces electricity or that it passes through. Some studies have shown no significant detrimental effect of ELF-MFs on biological systems, while other studies have shown that ELF-MFs increase the risk of the development of childhood leukaemia (1). Moreover, the 40 Hz-7mT range ELF-MF has been used as a magnetotherapy instrument (2). In this study, we aimed to compare the effect of ELFMF on healthy dermal fibroblasts and breast cancer cells (MCF7). Material and Method: After the administration of 1 mT-50 Hz ELF-MF to healthy and cancer cells for different exposure times, apoptosis/necrosis levels were investigated and cell cycles and proliferation indexes were examined. The Analytic Hierarchy Process (AHP) was applied to find the most effective dose. Results: The ELF-MF did not show any significant effect on MCF7 cells. However, it caused increased apoptosis and decreased proliferation of healthy fibroblast cells. Furthermore, no changes in the cell cycle were observed in either cell line. As a result of AHP, the most effective exposure was determined to be 1 hour. Conclusion: Our results showed that while the ELF-MF reduces the viability of healthy fibroblasts, it has not observed therapeutic effect on breast cancer cells.